Method and system for controlling parallel variable frequency water pump of refrigerating unit based on fuzzy algorithm

Abstract

The invention discloses a fuzzy algorithm-based control method and system for parallel variable-frequency water pumps of a refrigerating unit. The method comprises the following steps of: acquiring operation data of the refrigerating unit; and determining an input variable according to the operation data, determining an output variable through a fuzzy algorithm based on the input variable, and adjusting the refrigerating unit parallel variable frequency water pump according to the output variable. The fuzzy algorithm is adopted to control the refrigerating unit parallel variable frequency water pump, and the chilled water supply and return water temperature difference, the chilled water flow deviation, the cooling water supply and return water temperature difference, the cooling water flow deviation and the refrigerating unit load rate serve as input variables; the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount are used as output variables, so that the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount can be smoothly adjusted according to the current state and the change trend of the system, oscillation and overshoot are effectively reduced, the system runs more stably, and the service life of equipment is prolonged.

Description

Technical Field

[0001] The present application relates to the technical field of refrigeration systems, and particularly relates to a control method and system for parallel variable-frequency water pumps of a refrigeration unit based on a fuzzy algorithm. Background Art

[0002] With the continuous expansion of industrial production scale and the increasing number of commercial buildings and public facilities (such as shopping malls, hospitals, office buildings, etc.), the demand for refrigeration systems has also increased significantly. To meet the refrigeration requirements of large areas and high loads, the scale of refrigeration units has been continuously expanded, and a parallel water pump system has become a common configuration to provide sufficient flow rate and head to ensure the circulation of the refrigeration medium in the system and maintain the refrigeration effect. Modern refrigeration systems are becoming more and more complex, not only to meet the basic refrigeration requirements, but also to consider various factors such as temperature control, humidity adjustment, and air quality in different areas. This requires the parallel water pump system to be able to achieve more precise and flexible control to adapt to complex and changeable working conditions. However, when the existing control methods adjust the operating state of the water pump, oscillation and overshoot phenomena are likely to occur, which will not only affect the stability of the system, but also may cause equipment wear and energy waste.

[0003] Therefore, the existing technology still needs to be improved. Summary of the Invention

[0004] The technical problem to be solved by the present application is to provide a control method and system for parallel variable-frequency water pumps of a refrigeration unit based on a fuzzy algorithm in view of the deficiencies of the existing technology.

[0005] To solve the above technical problem, the first aspect of the present application provides a control method for parallel variable-frequency water pumps of a refrigeration unit based on a fuzzy algorithm. Specifically, the control method for parallel variable-frequency water pumps of a refrigeration unit based on a fuzzy algorithm includes:

[0006] Collect the operating data of the refrigeration unit, where the operating data includes the chilled water supply temperature, chilled water return temperature, actual chilled water flow rate, cooling water supply temperature, cooling water return temperature, actual cooling water flow rate, and the actual load of the refrigeration unit;

[0007] Determine the input variables according to the operating data, and determine the output variables based on the input variables through a fuzzy algorithm. The input variables include the chilled water supply and return temperature difference, chilled water flow deviation, cooling water supply and return temperature difference, cooling water flow deviation, and the load rate of the refrigeration unit. The output variables include the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount;

[0008] Adjust the parallel variable-frequency water pumps of the refrigeration unit according to the output variables.

[0009] The control method of the parallel variable-frequency water pumps of a refrigeration unit based on a fuzzy algorithm, wherein determining the output variable based on the input variable through the fuzzy algorithm specifically includes:

[0010] Determining the activation strength of each preset fuzzy rule in the preset fuzzy rule set based on the input variable;

[0011] Determining the fuzzy output variable according to the membership function of the chilled water pump frequency adjustment amount, the membership function of the cooling water pump frequency adjustment amount in each preset fuzzy rule, and the activation strength of each preset fuzzy rule;

[0012] Defuzzifying the fuzzy output variable by the centroid method to determine the output variable.

[0013] The control method of the parallel variable-frequency water pumps of a refrigeration unit based on a fuzzy algorithm, wherein the preset fuzzy rule set is constructed based on the fuzzy sets of the input variable and the output variable; the fuzzy sets of the input variable include:

[0014] Chilled water supply-return temperature difference = {"very small", "small", "medium", "large", "very large"};

[0015] Chilled water flow deviation = {"negative large", "negative small", "zero", "positive small", "positive large"};

[0016] Cooling water supply-return temperature difference = {"very small", "small", "medium", "large", "very large"};

[0017] Cooling water flow deviation = {"negative large", "negative small", "zero", "positive small", "positive large"};

[0018] Refrigeration unit load rate = {"low", "medium", "high"};

[0019] The fuzzy sets of the output variable include:

[0020] Chilled water pump frequency adjustment amount = {"substantially reduced", "moderately reduced", "slightly reduced", "unchanged", "slightly increased", "moderately increased", "substantially increased"};

[0021] Chilled water pump frequency adjustment amount = {"substantially reduced", "moderately reduced", "slightly reduced", "unchanged", "slightly increased", "moderately increased", "substantially increased"}.

[0022] The control method of the parallel variable-frequency water pumps of a refrigeration unit based on a fuzzy algorithm, wherein the temperature difference between the supply and return chilled water, the deviation of the chilled water flow rate, the temperature difference between the supply and return cooling water, and the deviation of the cooling water flow rate adopt Gaussian membership functions, the load rate of the refrigeration unit adopts a trapezoidal membership function, and the adjustment amount of the frequency of the chilled water pump and the adjustment amount of the frequency of the chilled water pump adopt triangular membership functions.

[0023] The control method of the parallel variable-frequency water pumps of a refrigeration unit based on a fuzzy algorithm, wherein, after adjusting the parallel variable-frequency water pumps of the refrigeration unit according to the adjustment amount of the frequency of the chilled water pump and the adjustment amount of the frequency of the cooling water pump, the method further includes:

[0024] Obtain the total energy consumption after adjustment and the total energy consumption before adjustment;

[0025] If the relationship between the total energy consumption after adjustment and the total energy consumption before adjustment meets the preset requirements, then re-execute the step of collecting the operation data of the refrigeration unit, wherein the preset requirements are that the total energy consumption after adjustment is higher than the total energy consumption before adjustment, and the change amount of the total energy consumption after adjustment relative to the total energy consumption before adjustment is greater than the preset threshold;

[0026] If the relationship between the total energy consumption after adjustment and the total energy consumption before adjustment does not meet the preset requirements, then execute the step of collecting the operation data of the refrigeration unit according to the preset interval period.

[0027] The control method of the parallel variable-frequency water pumps of a refrigeration unit based on a fuzzy algorithm, wherein, before adjusting the parallel variable-frequency water pumps of the refrigeration unit according to the output variable, the method includes:

[0028] Calculate the adjusted frequency of the chilled water pump and the frequency of the cooling water pump based on the output variable;

[0029] If both the adjusted frequency of the chilled water pump and the adjusted frequency of the cooling water pump meet the preset conditions, then adjust the parallel variable-frequency water pumps of the refrigeration unit according to the output variable;

[0030] If at least one of the adjusted frequency of the chilled water pump and the adjusted frequency of the cooling water pump does not meet the preset conditions, then do not execute the adjustment of the parallel variable-frequency water pumps of the refrigeration unit according to the output variable, and execute the step of collecting the operation data of the refrigeration unit according to the preset interval period.

[0031] The control method of the parallel variable-frequency water pumps of a refrigeration unit based on a fuzzy algorithm, wherein, before adjusting the parallel variable-frequency water pumps of the refrigeration unit according to the output variable, the method further includes:

[0032] Detect whether the refrigeration unit meets the preset constraint conditions, where the preset constraint conditions include one or more of a load constraint condition, a supply-return water temperature difference constraint condition, and a flow deviation constraint condition;

[0033] If the preset constraint conditions are met, adjust the parallel variable-frequency water pumps of the refrigeration unit according to the output variables;

[0034] If the preset constraint conditions are not met, first control the refrigeration unit according to the control mode corresponding to the unmet constraint conditions, and then adjust the parallel variable-frequency water pumps of the refrigeration unit according to the output variables.

[0035] The second aspect of the present application provides a control system for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm. Specifically, the control system for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm includes:

[0036] An acquisition module for acquiring the operation data of the refrigeration unit, where the operation data includes the chilled water supply temperature, the chilled water return temperature, the actual chilled water flow rate, the cooling water supply temperature, the cooling water return temperature, the actual cooling water flow rate, and the actual load of the refrigeration unit;

[0037] A fuzzy algorithm module for determining input variables according to the operation data and determining output variables based on the input variables through a fuzzy algorithm. The input variables include the chilled water supply-return water temperature difference, the chilled water flow deviation, the cooling water supply-return water temperature difference, the cooling water flow deviation, and the refrigeration unit load rate, and the output variables include the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount;

[0038] A control module for adjusting the parallel variable-frequency water pumps of the refrigeration unit according to the output variables.

[0039] The third aspect of the present application provides a computer-readable storage medium storing one or more programs, and the one or more programs can be executed by one or more processors to implement the steps in any one of the above-mentioned control methods for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm.

[0040] The fourth aspect of the present application provides a terminal device, which includes: a processor and a memory;

[0041] The memory stores a computer-readable program executable by the processor;

[0042] When the processor executes the computer-readable program, it implements the steps in any one of the above-mentioned control methods for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm.

[0043] Beneficial effects: Compared with the prior art, the present application provides a control method and system for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm. The method includes collecting the operating data of the refrigeration unit; determining input variables according to the operating data, and determining output variables based on the input variables through a fuzzy algorithm, and adjusting the parallel variable-frequency water pump of the refrigeration unit according to the output variables. The present application controls the parallel variable-frequency water pump of the refrigeration unit by using a fuzzy algorithm, and uses the temperature difference between the supply and return water of chilled water, the deviation of chilled water flow rate, the temperature difference between the supply and return water of cooling water, the deviation of cooling water flow rate, and the load rate of the refrigeration unit as input variables, and uses the adjustment amount of the frequency of the chilled water pump and the adjustment amount of the frequency of the cooling water pump as output variables. In this way, according to the current state and change trend of the system, the adjustment amount of the frequency of the chilled water pump and the adjustment amount of the frequency of the cooling water pump can be smoothly adjusted, effectively reducing oscillation and overshoot, making the operation of the system more stable, and extending the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0045] Figure 1 It is a flowchart of the control method for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm provided by an embodiment of the present application.

[0046] Figure 2 It is a schematic flowchart of a specific example of the control method for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm provided by an embodiment of the present application.

[0047] Figure 3 It is a principle block diagram of a control device for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm provided by an embodiment of the present application.

[0048] Figure 4 It is a principle block diagram of a terminal device provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] The embodiments of the present application provide a control method and system for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm. To make the purpose, technical solutions and effects of the present application clearer and more definite, the following further details the present application with reference to the accompanying drawings and by way of examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0050] Those skilled in the art can understand that, unless specifically stated otherwise, the singular forms "a", "an", "the" and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of this application means the presence of the stated features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. It should be understood that when we say that an element is "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, or there may also be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or wireless coupling. The phrase "and / or" used herein includes all or any unit and all combinations of one or more related listed items.

[0051] Those skilled in the art can understand that, unless otherwise defined, all terms used herein (including technical terms and scientific terms) have the same meaning as the general understanding of those of ordinary skill in the art to which this application belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless specifically defined as here.

[0052] It should be understood that the sequence numbers and magnitudes of the steps in this embodiment do not mean the order of execution. The order of execution of each process is determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0053] Through research, it has been found that with the continuous expansion of the scale of industrial production and the increasing number of commercial buildings and public facilities (such as shopping malls, hospitals, office buildings, etc.), the demand for refrigeration systems has also increased significantly. To meet the refrigeration requirements of large areas and high loads, the scale of refrigeration units has been continuously expanded, and a parallel water pump system has become a common configuration method to provide sufficient flow and head to ensure the circulation of the refrigeration medium in the system and maintain the refrigeration effect. Modern refrigeration systems are becoming increasingly complex, not only to meet the basic refrigeration requirements, but also to consider various factors such as temperature control, humidity adjustment, and air quality in different areas. This requires the parallel water pump system to be able to achieve more precise and flexible control to adapt to complex and changeable working conditions.

[0054] The control methods of existing water pumps include traditional control methods and intelligent control methods. Traditional control is divided into on-off control and constant-frequency control. On-off control is based on the operating requirements of the refrigeration unit. When the set temperature or pressure threshold is reached, the start and stop of the water pump are directly controlled through a relay or contactor. This method has a simple control logic and low cost, but it cannot accurately adjust the operating state of the water pump. Constant-frequency control is to control the water pump to work at the rated power in the refrigeration system. Although this method can ensure a certain flow supply, it cannot flexibly adjust the output of the water pump when the system load changes, which is likely to cause energy waste.

[0055] Intelligent control methods are divided into variable-frequency control and group control. Variable-frequency control is to use sensors to continuously monitor parameters such as the temperature, pressure, and flow rate of the refrigeration system in real time. The frequency converter automatically adjusts the speed of the water pump according to the parameter information, so that the output of the water pump precisely matches the system load. The group control system is to reasonably allocate the operating tasks of each water pump according to the total load demand of the system through a central controller to achieve the optimized combined operation of the water pumps. Although these two methods can perform intelligent control on the water pump, they both rely on a large number of devices such as sensors, controllers, and communication networks. This not only requires a large amount of hardware costs, but also the design, installation, commissioning, and maintenance of the system require professional technical personnel and high cost investment. At the same time, when these two methods control the water pump, oscillation and overshoot phenomena are likely to occur, which will not only affect the stability of the system, but also may cause equipment wear and energy waste.

[0056] To solve the above problems, in the embodiments of the present application, the operating data of the refrigeration unit are collected; input variables are determined according to the operating data, and output variables are determined based on the input variables through a fuzzy algorithm, and the parallel variable-frequency water pumps of the refrigeration unit are adjusted according to the output variables. The present application controls the parallel variable-frequency water pumps of the refrigeration unit by using a fuzzy algorithm, and uses the chilled water supply-return temperature difference, chilled water flow deviation, cooling water supply-return temperature difference, cooling water flow deviation, and refrigeration unit load rate as input variables, and uses the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount as output variables. In this way, according to the current state and change trend of the system, the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount can be smoothly adjusted, effectively reducing oscillation and overshoot, making the operation of the system more stable, and extending the service life of the equipment.

[0057] The following further illustrates the application content through the description of embodiments in conjunction with the accompanying drawings.

[0058] This embodiment provides a control method for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm, as Figure 1 shown, the method includes:

[0059] S10. Collect the operating data of the refrigeration unit.

[0060] Specifically, the refrigeration unit is configured with parallel variable-frequency water pumps for preparing chilled water and cooling water. Among them, the operation data is collected during the operation of the intelligent unit through sensing devices (such as temperature sensors, flow meters, etc.), including the chilled water supply temperature, chilled water return temperature, actual chilled water flow rate, cooling water supply temperature, cooling water return temperature, actual cooling water flow rate, and the actual load of the refrigeration unit. Among them, when collecting the operation data of the refrigeration unit, the collection operation can be triggered by a collection instruction, and the collection instruction can be automatically generated according to a preset interval period, or can be generated based on a collection start operation, or can also be generated through a physical button.

[0061] S20. Determine the input variables according to the operation data, and determine the output variables based on the input variables through a fuzzy algorithm.

[0062] Specifically, the input variables are determined based on the operation data, and the output variables are the adjustment amounts for adjusting the parallel variable-frequency water pumps. The input variables include the chilled water supply and return temperature difference, chilled water flow deviation, cooling water supply and return temperature difference, cooling water flow deviation, and the load rate of the refrigeration unit. Among them, the chilled water supply and return temperature difference is used to reflect the cooling load of the chilled water system, which is determined by calculating the temperature difference between the chilled water supply temperature and the chilled water return temperature; the chilled water flow deviation is used to reflect the change in the flow demand of the chilled water system, which is calculated by calculating the difference between the actual chilled water flow rate and the set chilled water flow rate; the cooling water supply and return temperature difference is used to reflect the heat load of the cooling water system, which is determined by calculating the temperature difference between the cooling water supply temperature and the cooling water return temperature; the cooling water flow deviation is used to reflect the change in the flow demand of the cooling water system, which is calculated by calculating the difference between the actual cooling water flow rate and the set cooling water flow rate; the load rate of the refrigeration unit is used to represent the proportion of the current working load of the refrigeration unit to its rated load, which is determined by calculating the ratio of the actual load of the refrigeration unit to the rated load. The output variables include the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount. Among them, the chilled water pump frequency adjustment amount is used to adjust the operating frequency of the chilled water pump, and the cooling water pump frequency adjustment amount is used to adjust the operating frequency of the cooling water pump.

[0063] The fuzzy algorithm does not require an accurate mathematical model. It summarizes and refines the experience and knowledge of human experts, describes the input-output relationship of the system in the form of fuzzy rules, and then determines the output variables based on this input-output relationship, enabling it to well adapt to the control requirements of complex systems. Based on this, as Figure 2 shown, the determining of the output variables based on the input variables through a fuzzy algorithm specifically includes:

[0064] Determine the activation strength of each preset fuzzy rule in the preset fuzzy rule set based on the input variables;

[0065] Determine the fuzzy output variables according to the membership functions of the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount in each preset fuzzy rule and the activation strength of each preset fuzzy rule;

[0066] Defuzzify the fuzzy output variables by the centroid method to determine the output variables.

[0067] Specifically, the preset fuzzy rule set is constructed based on the fuzzy sets of the input variables and the output variables. That is, before determining the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount through the fuzzy algorithm, the temperature difference between the supply and return water of the chilled water, the deviation of the chilled water flow rate, the temperature difference between the supply and return water of the cooling water, the deviation of the cooling water flow rate, and the load rate of the refrigeration unit are used as input variables, and the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount are used as output variables. Then, the input variables and the output variables are fuzzified to form the fuzzy sets of the input variables and the fuzzy sets of the output variables.

[0068] Furthermore, when fuzzifying the input variables and the output variables, the interval thresholds of fuzzification corresponding to the input variables and the output variables can be determined by summarizing and refining the experience and knowledge of human experts. Then, the input variables and the output variables are fuzzified according to the interval thresholds of fuzzification corresponding to them. Among them, the interval thresholds of fuzzification can be determined according to prior knowledge, and no specific limitation is made here, only the fuzzy sets corresponding to the input variables and the output variables are given. Specifically, the fuzzy set of the input variables includes:

[0069] Temperature difference between the supply and return water of the chilled water = {"very small (VS)", "small (S)", "medium (M)", "large (L)", "very large (VL)"};

[0070] Deviation of the chilled water flow rate = {"negative large (NB)", "negative small (NS)", "zero (Z)", "positive small (PS)", "positive large (PB)"};

[0071] Temperature difference between the supply and return water of the cooling water = {"very small (VS)", "small (S)", "medium (M)", "large (L)", "very large (VL)"};

[0072] Deviation of the cooling water flow rate = {"negative large (NB)", "negative small (NS)", "zero (Z)", "positive small (PS)", "positive large (PB)"};

[0073] Load rate of the refrigeration unit = {"low (Ld)", "medium (Md)", "high (Hd)"};

[0074] The fuzzy set of the output variables includes:

[0075] Chilled water pump frequency adjustment amount = {"Substantially decreased (VLD)", "Moderately decreased (LD)", "Slightly decreased (SD)", "Unchanged (S)", "Slightly increased (SU)", "Moderately increased (LU)", "Substantially increased (VLU)"};

[0076] Chilled water pump frequency adjustment amount = {"Substantially decreased (VLD)", "Moderately decreased (LD)", "Slightly decreased (SD)", "Unchanged (S)", "Slightly increased (SU)", "Moderately increased (LU)", "Substantially increased (VLU)"}.

[0077] Furthermore, after constructing fuzzy sets for the input variables and output variables, the membership functions adopted for each fuzzy set are also determined. Among them, the chilled water supply - return temperature difference, the chilled water flow deviation, the cooling water supply - return temperature difference, and the cooling water flow deviation adopt Gaussian - type membership functions, the chiller load rate adopts a trapezoidal membership function, and the chilled water pump frequency adjustment amount and the chilled water pump frequency adjustment amount adopt triangular membership functions. Among them, the chilled water supply - return temperature difference and the cooling water supply - return temperature difference adopt the same membership function, the chilled water flow deviation and the cooling water flow deviation adopt the same membership function, and the chilled water pump frequency adjustment amount and the chilled water pump frequency adjustment amount adopt the same membership function. Therefore, the membership functions of each fuzzy set of the chilled water supply - return temperature difference, the chilled water flow deviation, and the chiller load rate can be described here.

[0078] Chilled water supply - return temperature difference ΔT ch Membership functions of each fuzzy set:

[0079]

[0080] For "Small S": Membership function For "Medium M": Membership function For "Large L": Membership function For "Very large VL": Membership function Among them, c i and σ i are parameters determined according to the actual system, i = 1, 2, 3, 4, 5, ΔT ch represents the chilled water supply - return temperature difference. Chilled water flow deviation ΔQ ch Membership functions of each fuzzy set:

[0081] For "Negative large NB": Membership function For "Negative small NS": Membership function For "Zero Z": Membership function For "Positive small PS": Membership function For "Zhengda PB": Membership function where c i and σ i are parameters determined according to the actual system, i = 6, 7, 8, 9, 10, and ΔQ ch represents the chilled water flow deviation. The membership functions of the fuzzy sets of the chiller load rate L are as follows:

[0082] For "Low Ld": Membership function

[0083] For "Medium (Md)": Membership function

[0084] For "High (Hd)": Membership function

[0085] where a i is a parameter determined according to the actual system, i = 1, 2, 3, 4, 5, 6, and L represents the chiller load rate.

[0086] Taking into account the influence of each input variable on the output variable, a preset fuzzy rule set is formulated. For example, the preset fuzzy rule set includes 375 preset fuzzy rules, which can be expressed as:

[0087] Rule number <![CDATA[ΔT ch > <![CDATA[ΔQ ch > <![CDATA[ΔT cw > <![CDATA[ΔT cw > L <![CDATA[Δf ch > <![CDATA[Δf cw > 1 VS NB VS NB Ld VLD VLD 2 VS NB VS NS Ld VLD LD 3 VS NB VS Z Ld VLD LD ··· ··· ··· ··· ··· ··· ··· ··· 375 VL PB VL PB Hd VLU VLU

[0088] Furthermore, the activation strength of each preset fuzzy rule can be expressed as:

[0089]

[0090] where are the membership degrees of the corresponding input variables in each preset fuzzy rule respectively, ω i represents the activation strength, and ∧ represents the minimum operation.

[0091] After obtaining the activation strength of each preset fuzzy rule, the output membership function of each preset fuzzy rule is calculated based on the activation strength of each preset fuzzy rule. Among them, the output membership function includes the output membership function of the chilled water pump frequency adjustment amount Δf ch and the output membership function of the chilled water pump frequency adjustment amount Δf and the output membership function of the chilled water pump frequency adjustment amount Δf cw and and can be:

[0092]

[0093] where represents the membership degree of the chilled water pump frequency adjustment amount in the i-th preset fuzzy rule. Denote the membership degree of the frequency adjustment amount of the chilled water pump in the i-th preset fuzzy rule.

[0094] Furthermore, the process of defuzzifying the fuzzy output variable by the centroid method can be expressed as:

[0095]

[0096] where ∨ represents the maximum operation, denotes the frequency adjustment amount of the chilled water pump calculated by the fuzzy algorithm, denotes the frequency adjustment amount of the cooling water pump calculated by the fuzzy algorithm.

[0097] S30. Adjust the parallel variable-frequency pumps of the refrigeration unit according to the output variable.

[0098] Specifically, after obtaining the output variable, adjust the operating frequency of the chilled water pump based on the frequency adjustment amount of the chilled water pump, and adjust the operating frequency of the cooling water pump based on the frequency adjustment amount of the cooling water pump to achieve the control of the parallel variable-frequency pumps of the refrigeration unit. In addition, when adjusting the parallel variable-frequency pumps of the refrigeration unit, it is possible to first detect whether the refrigeration unit meets the preset constraint conditions, and then adjust the parallel variable-frequency pumps of the refrigeration unit according to the detection results.

[0099] Based on this, before adjusting the parallel variable-frequency pumps of the refrigeration unit according to the output variable, the method further includes:

[0100] Detect whether the refrigeration unit meets the preset constraint conditions;

[0101] If the preset constraint conditions are met, adjust the parallel variable-frequency pumps of the refrigeration unit according to the output variable;

[0102] If the preset constraint conditions are not met, first control the refrigeration unit according to the control method corresponding to the unmet constraint conditions, and then adjust the parallel variable-frequency pumps of the refrigeration unit according to the output variable.

[0103] Specifically, the preset constraint conditions are pre-set, and may include one or more of a load constraint condition, a supply-return water temperature difference constraint condition, and a flow deviation constraint condition. Among them, the load constraint condition is used to limit the load rate of the refrigeration unit to avoid reducing efficiency and increasing energy consumption due to too high or too low load rate of the refrigeration unit. For example, during normal operation, the load rate should be maintained at 40%-90%. When the load rate is lower than 40%, the number of operating refrigeration units can be appropriately reduced; when it is higher than 90%, it is necessary to consider starting the standby unit to avoid long-term high-load operation of a single unit. The supply-return water temperature difference constraint condition is used to limit the supply-return water temperature difference of chilled water and cooling water, so that the supply-return water temperature difference of chilled water and cooling water needs to be maintained within a preset range. For example, the supply-return water temperature difference of chilled water is usually about 5°C, and the allowable fluctuation range is ±1°C. Too small a temperature difference may indicate problems such as uneven distribution of cooling capacity in the system or low heat exchange efficiency of equipment; too large a temperature difference will increase the energy consumption of the water pump and the burden on the equipment. When the temperature difference is too small or too large, a warning message can be generated. The flow deviation constraint condition is used to limit the flow deviation of chilled water and cooling water, so that the deviation between the actual flow rate and the set flow rate of chilled water and cooling water should be controlled within a set range. For example, if the set range is ±10%, then too large a deviation will affect the hydraulic balance and refrigeration effect of the system, resulting in increased energy consumption. Therefore, when the flow deviation exceeds the range, it can be corrected by adjusting the frequency of the water pump or the opening of the valve.

[0104] It should be noted that the control method corresponding to the constraint condition can be pre-set. Here, the control method corresponding to the constraint condition is not restricted, and only specific examples are given for illustration. For example, the control method corresponding to the load constraint condition can be to reduce the number of operating refrigeration units when the load rate is lower than the load rate range corresponding to the load constraint condition; when the load rate is higher than the load rate range corresponding to the load constraint condition, start the standby unit; the control method corresponding to the supply-return water temperature difference constraint condition can be to generate a warning message; the control method corresponding to the flow deviation constraint condition can be to adjust the frequency of the water pump or the opening of the valve when the flow deviation exceeds the range. In addition, after first controlling the refrigeration unit according to the control method corresponding to the unmet constraint condition, the parallel variable-frequency water pump of the refrigeration unit can be directly adjusted according to the output variable, or the operation data of the refrigeration unit can be collected again.

[0105] In one implementation, in addition to using the above preset constraint conditions to constrain the refrigeration unit, a frequency constraint condition can also be set so that the operating frequencies of the chilled water pump and the cooling water pump are both within a set frequency range. Based on this, before adjusting the parallel variable-frequency water pump of the refrigeration unit according to the output variable, the method includes:

[0106] Calculating the adjusted operating frequencies of the chilled water pump and the cooling water pump based on the output variable;

[0107] If both the adjusted frequency of the chilled water pump and the adjusted frequency of the cooling water pump meet the preset conditions, then adjust the parallel variable-frequency pumps of the refrigeration unit according to the output variable;

[0108] If at least one of the adjusted frequency of the chilled water pump and the adjusted frequency of the cooling water pump does not meet the preset conditions, then do not perform the adjustment of the parallel variable-frequency pumps of the refrigeration unit according to the output variable, and perform the step of collecting the operating data of the refrigeration unit at preset interval periods.

[0109] Specifically, the preset conditions are pre-set and used to limit the operating frequencies of the chilled water pump and the cooling water pump so that the operating frequencies of the chilled water pump and the cooling water pump are both within the preset frequency range. For example, the preset condition is the preset frequency range. When the adjusted frequency of the chilled water pump and the adjusted frequency of the cooling water pump are within this preset frequency range, it means that both the adjusted frequency of the chilled water pump and the adjusted frequency of the cooling water pump meet the preset conditions. On the contrary, when the adjusted frequency of the chilled water pump is not within this preset frequency range, it means that the adjusted frequency of the chilled water pump does not meet the requirements. When the adjusted frequency of the cooling water pump is not within this preset frequency range, it means that the adjusted frequency of the cooling water pump does not meet the requirements.

[0110] Furthermore, when at least one of the adjusted frequency of the chilled water pump and the adjusted frequency of the cooling water pump does not meet the preset conditions, it means that the parallel variable-frequency pumps of the refrigeration unit do not meet the requirements. At this time, it is necessary not to perform the adjustment of the parallel variable-frequency pumps of the refrigeration unit according to the output variable, and perform the step of collecting the operating data of the refrigeration unit at preset interval periods to avoid the operating frequencies of the cooling water pump and the chilled water pump being too high or too low.

[0111] In one implementation, when controlling the operating frequencies of the cooling water pump and the chilled water pump, the control process of the operating frequencies of the cooling water pump and the chilled water pump can be targeted at the lowest total energy consumption. Correspondingly, after adjusting the parallel variable-frequency pumps of the refrigeration unit according to the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount, the method further includes:

[0112] Obtain the total energy consumption after adjustment and the total energy consumption before adjustment;

[0113] If the relationship between the total energy consumption after adjustment and the total energy consumption before adjustment meets the preset requirements, then re-perform the step of collecting the operating data of the refrigeration unit;

[0114] If the relationship between the total energy consumption after adjustment and the total energy consumption before adjustment does not meet the preset requirements, then perform the step of collecting the operating data of the refrigeration unit at preset interval periods.

[0115] Specifically, the total energy consumption refers to the energy consumption of the chilled water pump and the cooling water pump. That is to say, the adjusted total energy consumption refers to the sum of the adjusted energy consumption of the chilled water pump and the adjusted energy consumption of the cooling water pump, and the total energy consumption before adjustment refers to the sum of the energy consumption of the chilled water pump before adjustment and the energy consumption of the cooling water pump before adjustment. Here, taking the adjusted total energy consumption as an example, the process of obtaining the total energy consumption is described. The power P of the chilled water pump ch is related to the operating frequency f of the chilled water pump ch and usually (according to the pump similarity law), assuming the operating frequency before adjustment is f ch0 , and the operating frequency after adjustment is then the energy consumption of the chilled water pump where k ch is the coefficient related to the pump characteristics, and t is the operating time. Similarly, the energy consumption of the adjusted cooling water pump Then the adjusted total energy consumption E = E ch + E cw . In addition, the total energy consumption before adjustment can be directly retrieved from the calculation during the previous adjustment or recalculated during the current adjustment.

[0116] Furthermore, in the embodiments of the present application, the operating frequencies of the chilled water pump and the cooling water pump are adjusted with the goal of minimizing the total energy consumption. Therefore, after obtaining the adjusted total energy consumption and the total energy consumption before adjustment, the adjusted total energy consumption and the total energy consumption before adjustment can be compared to determine whether the current adjustment will achieve a reduction in the total energy consumption so that the total energy consumption tends to be the lowest. Correspondingly, it will be determined that the relationship between the adjusted total energy consumption and the total energy consumption before adjustment does not meet the preset requirements, where the preset requirements are used to ensure that the total energy consumption tends to be the lowest. For example, the preset requirement is that the adjusted total energy consumption is higher than the total energy consumption before adjustment, and the change amount of the adjusted total energy consumption relative to the total energy consumption before adjustment is greater than the preset threshold, and the preset threshold is pre-set, for example, 5% or the like. Then, if the preset requirements are met, the data acquisition step is immediately returned, and the operating frequencies of the chilled water pump and the cooling water pump are readjusted to reduce the operating time of high energy consumption. On the contrary, if the preset requirements are not met, the adjusted operating frequency is maintained for operation, and the next data acquisition moment is waited for at the preset interval time.

[0117] In summary, this embodiment provides a control method for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm. The method includes collecting the operation data of the refrigeration unit; determining input variables according to the operation data, and determining output variables based on the input variables through a fuzzy algorithm, and adjusting the parallel variable-frequency water pump of the refrigeration unit according to the output variables. In this application, a fuzzy algorithm is used to control the parallel variable-frequency water pump of the refrigeration unit, and the temperature difference between the supply and return water of the chilled water, the deviation of the chilled water flow rate, the temperature difference between the supply and return water of the cooling water, the deviation of the cooling water flow rate, and the load rate of the refrigeration unit are used as input variables, and the adjustment amount of the chilled water pump frequency and the adjustment amount of the cooling water pump frequency are used as output variables. In this way, according to the current state and change trend of the system, the adjustment amount of the chilled water pump frequency and the adjustment amount of the cooling water pump frequency can be smoothly adjusted, effectively reducing oscillation and overshoot, making the operation of the system more stable, and extending the service life of the equipment.

[0118] Based on the above control method for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm, this embodiment provides a control system for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm, as Figure 3 shown. The control system for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm specifically includes:

[0119] An acquisition module 100, configured to collect the operation data of the refrigeration unit, where the operation data includes the chilled water supply temperature, the chilled water return temperature, the actual chilled water flow rate, the cooling water supply temperature, the cooling water return temperature, the actual cooling water flow rate, and the actual load of the refrigeration unit;

[0120] A fuzzy algorithm module 200, configured to determine input variables according to the operation data, and determine output variables based on the input variables through a fuzzy algorithm, where the input variables include the temperature difference between the supply and return water of the chilled water, the deviation of the chilled water flow rate, the temperature difference between the supply and return water of the cooling water, the deviation of the cooling water flow rate, and the load rate of the refrigeration unit, and the output variables include the adjustment amount of the chilled water pump frequency and the adjustment amount of the cooling water pump frequency;

[0121] A control module 300, configured to adjust the parallel variable-frequency water pump of the refrigeration unit according to the output variables.

[0122] Based on the above control method for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm, this embodiment provides a computer-readable storage medium. The computer-readable storage medium stores one or more programs, and the one or more programs can be executed by one or more processors to implement the steps in the control method for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm as described in the above embodiment.

[0123] Based on the above control method for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm, this application also provides a terminal device, asFigure 4 As shown in the figure, it includes at least one processor 20; a display screen 21; and a memory 22, and may also include a communication interface 23 and a bus 24. Among them, the processor 20, the display screen 21, the memory 22, and the communication interface 23 can complete communication with each other through the bus 24. The display screen 21 is set to display a user guidance interface preset in the initial setting mode. The communication interface 23 can transmit information. The processor 20 can call the logical instructions in the memory 22 to execute the methods in the above embodiments.

[0124] In addition, when the logical instructions in the above-mentioned memory 22 are implemented in the form of a software functional unit and sold or used as an independent product, they can be stored in a computer-readable storage medium.

[0125] The memory 22, as a computer-readable storage medium, can be set to store software programs and computer-executable programs, such as the program instructions or modules corresponding to the methods in the embodiments of the present disclosure. The processor 20 executes functional applications and data processing by running the software programs, instructions, or modules stored in the memory 22, that is, implements the methods in the above embodiments.

[0126] The memory 22 may include a program storage area and a data storage area. Among them, the program storage area can store an operating system and application programs required for at least one function; the data storage area can store data created according to the use of the terminal device, etc. In addition, the memory 22 may include a high-speed random access memory and may also include a non-volatile memory. For example, various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disc, can also be a transient storage medium.

[0127] In addition, the specific processes of loading and executing multiple instructions by the above-mentioned storage medium and the instruction processor in the terminal device have been described in detail in the above methods, and will not be repeated here one by one.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A control method for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm, characterized in that, The control method of the parallel variable-frequency water pumps of the refrigeration unit based on the fuzzy algorithm specifically includes: Collect the operation data of the refrigeration unit, where the operation data includes the chilled water supply temperature, the chilled water return temperature, the actual chilled water flow rate, the cooling water supply temperature, the cooling water return temperature, the actual cooling water flow rate, and the actual load of the refrigeration unit; Determine the input variables according to the operation data, and determine the output variables based on the input variables through the fuzzy algorithm. Among them, the input variables include the chilled water supply-return temperature difference, the chilled water flow rate deviation, the cooling water supply-return temperature difference, the cooling water flow rate deviation, and the refrigeration unit load rate, and the output variables include the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount; Adjust the parallel variable-frequency water pumps of the refrigeration unit according to the output variables.

2. The control method of the parallel variable-frequency water pump of the refrigeration unit based on the fuzzy algorithm according to claim 1, characterized in that, The specific process of determining the output variables based on the input variables through the fuzzy algorithm includes: Determine the activation strength of each preset fuzzy rule in the preset fuzzy rule set based on the input variables; Determine the fuzzy output variables according to the membership function of the chilled water pump frequency adjustment amount, the membership function of the cooling water pump frequency adjustment amount in each preset fuzzy rule, and the activation strength of each preset fuzzy rule; Defuzzify the fuzzy output variables by the centroid method to determine the output variables.

3. The control method of the parallel variable-frequency water pump of the refrigeration unit based on the fuzzy algorithm according to claim 2, characterized in that, The preset fuzzy rule set is constructed based on the fuzzy sets of the input variables and the output variables; The fuzzy sets of the input variables include: Chilled water supply-return temperature difference = {"very small", "small", "medium", "large", "very large"}; Chilled water flow rate deviation = {"negative large", "negative small", "zero", "positive small", "positive large"}; Cooling water supply-return temperature difference = {"very small", "small", "medium", "large", "very large"}; Cooling water flow rate deviation = {"negative large", "negative small", "zero", "positive small", "positive large"}; Refrigeration unit load rate = {"low", "medium", "high"}; The fuzzy sets of the output variables include: Chilled water pump frequency adjustment amount = {"substantially reduced", "moderately reduced", "slightly reduced", "unchanged", "slightly increased", "moderately increased", "substantially increased"}; Cooling water pump frequency adjustment amount = {"substantially reduced", "moderately reduced", "slightly reduced", "unchanged", "slightly increased", "moderately increased", "substantially increased"}.

4. The control method of the parallel variable-frequency water pump of the refrigeration unit based on the fuzzy algorithm according to claim 3, characterized in that, The Gaussian membership function is used for the chilled water supply-return temperature difference, the chilled water flow rate deviation, the cooling water supply-return temperature difference, and the cooling water flow rate deviation, the trapezoidal membership function is used for the refrigeration unit load rate, and the triangular membership function is used for the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount.

5. The control method of the parallel variable-frequency water pump of the refrigeration unit based on the fuzzy algorithm according to claim 1, characterized in that After adjusting the parallel variable-frequency water pumps of the refrigeration unit according to the chilled water pump frequency adjustment amount and the cooling water pump frequency adjustment amount, the method further includes: Obtain the total energy consumption after adjustment and the total energy consumption before adjustment; If the relationship between the total energy consumption after adjustment and the total energy consumption before adjustment meets the preset requirements, the step of collecting the operation data of the refrigeration unit is re-executed, where the preset requirements are that the total energy consumption after adjustment is higher than the total energy consumption before adjustment, and the change amount of the total energy consumption after adjustment relative to the total energy consumption before adjustment is greater than the preset threshold; If the relationship between the total energy consumption after adjustment and the total energy consumption before adjustment does not meet the preset requirements, the step of collecting the operation data of the refrigeration unit is executed at a preset interval period.

6. The control method of the parallel variable-frequency water pump of the refrigeration unit based on the fuzzy algorithm according to claim 1, characterized in that, Before adjusting the parallel variable-frequency water pumps of the refrigeration unit according to the output variable, the method includes: Calculating the adjusted chilled water pump frequency and cooling water pump frequency based on the output variable; If both the adjusted chilled water pump frequency and the adjusted cooling water pump frequency meet the preset conditions, the parallel variable-frequency water pumps of the refrigeration unit are adjusted according to the output variable; If at least one of the adjusted chilled water pump frequency and the adjusted cooling water pump frequency does not meet the preset conditions, the adjustment of the parallel variable-frequency water pumps of the refrigeration unit according to the output variable is not performed, and the step of collecting the operation data of the refrigeration unit is executed at a preset interval period.

7. The control method of the parallel variable-frequency water pump of the refrigeration unit based on the fuzzy algorithm according to claim 1 or 6, characterized in that, Before adjusting the parallel variable-frequency water pumps of the refrigeration unit according to the output variable, the method further includes: Detecting whether the refrigeration unit meets the preset constraint conditions, where the preset constraint conditions include one or more of a load constraint condition, a supply-return water temperature difference constraint condition, and a flow deviation constraint condition; If the preset constraint conditions are met, the parallel variable-frequency water pumps of the refrigeration unit are adjusted according to the output variable; If the preset constraint conditions are not met, the refrigeration unit is first controlled according to the control mode corresponding to the unmet constraint condition, and then the parallel variable-frequency water pumps of the refrigeration unit are adjusted according to the output variable.

8. A control system for a parallel variable-frequency water pump of a refrigeration unit based on a fuzzy algorithm, characterized in that, The control system of the parallel variable-frequency water pumps of the refrigeration unit based on the fuzzy algorithm specifically includes: A collection module for collecting the operation data of the refrigeration unit, where the operation data includes chilled water supply temperature, chilled water return temperature, actual chilled water flow, cooling water supply temperature, cooling water return temperature, actual cooling water flow, and actual load of the refrigeration unit; A fuzzy algorithm module for determining input variables according to the operation data and determining output variables based on the input variables through the fuzzy algorithm, where the input variables include chilled water supply-return temperature difference, chilled water flow deviation, cooling water supply-return temperature difference, cooling water flow deviation, and refrigeration unit load rate, and the output variables include chilled water pump frequency adjustment amount and cooling water pump frequency adjustment amount; A control module for adjusting the parallel variable-frequency water pumps of the refrigeration unit according to the output variable.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores one or more programs, and the one or more programs can be executed by one or more processors to implement the steps in the control method of the parallel variable-frequency water pumps of the refrigeration unit based on the fuzzy algorithm as described in any one of claims 1-7.

10. A terminal device, characterized in that, Including: A processor and a memory; The memory stores a computer-readable program executable by the processor; When the processor executes the computer-readable program, it implements the steps in the control method of the parallel variable-frequency water pumps of the refrigeration unit based on the fuzzy algorithm described in any one of claims 1-7.

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