Energy-saving control method and system for water chilling unit

Abstract

The invention relates to the technical field of general control systems, in particular to a water chilling unit energy-saving control method and system.The method comprises the steps that the machining process of a numerical control machine tool is equally divided into a plurality of monitoring time periods, and the demand degree of a water chilling unit in the machining process of the numerical control machine tool in the monitoring time periods is determined to screen out a target monitoring time period; energy consumption of the water chilling unit in the target monitoring time period is determined in combination with the time interval from the moment after the cutting temperature rises to the moment when the rotating speed of the compressor changes, and then the cooling effect of the water chilling unit in the target monitoring time period is determined in combination with rising changes of the cutting temperature and the environment temperature. And determining a regulation and control coefficient of the variable frequency driving control system in the target monitoring time period, and regulating and controlling the running speed of a compressor of the water chilling unit. The regulation and control coefficient for energy-saving control of the water chilling unit in the frequency conversion control system is obtained, and the operation speed of the compressor of the water chilling unit is regulated and controlled, so that the purpose of energy-saving control of the water chilling unit is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of general control systems, and particularly to an energy-saving control method and system for a water chiller. Background Art

[0002] Water chillers are mainly used to provide low-temperature cooling water and are widely used in air-conditioning systems, industrial cooling, food processing and other fields. With the development of the economy, the usage frequency and load fluctuation of water chillers have increased significantly, resulting in a continuous rise in their energy consumption. According to statistics, the energy efficiency ratio of water chillers is affected by environmental temperature, load changes and the operating state of the unit during operation. In order to reduce energy consumption and improve the energy utilization efficiency of the system, it is urgent to implement effective energy-saving control for water chillers.

[0003] Existing problems: Although the existing energy-saving control methods for water chillers have achieved energy conservation and consumption reduction to a certain extent, there are still some deficiencies. For example, in the existing energy-saving control methods, during the operation of the water chiller, the distribution of cold and hot water in the water circulation system may be uneven, which may lead to unstable cooling effect of the evaporator. And during the exchange of cold and hot water, the heat transfer efficiency of the heat exchanger may be reduced due to water quality, resulting in insufficient heat exchange. In this state, the refrigerant cannot effectively absorb heat, thus affecting the refrigeration capacity of the water chiller and further increasing the energy consumption of the water chiller. Summary of the Invention

[0004] The present invention provides an energy-saving control method and system for a water chiller to solve the existing problems.

[0005] An energy-saving control method and system for a water chiller of the present invention adopts the following technical solutions:

[0006] An embodiment of the present invention provides an energy-saving control method for a water chiller, and the method includes the following steps:

[0007] During the machining process of a numerically controlled machine tool, obtain the cutting force, cutting temperature, machine tool vibration data, inlet water temperature, outlet water temperature, compressor speed, environmental temperature of the water chiller at each moment, and the moment when the compressor speed changes each time;

[0008] Divide the machining process of the numerically controlled machine tool into several monitoring periods equally; determine the demand degree of the water chiller during the machining process of the numerically controlled machine tool within the monitoring period according to the changes of the cutting force, cutting temperature and machine tool vibration data within the monitoring period;

[0009] According to the magnitude of the demand degree, screen out the target monitoring periods; determine the cooling effect of the water chiller in the target monitoring periods according to the rising change of the cutting temperature and the difference between the inlet water temperature and the outlet water temperature of the water chiller within the target monitoring periods;

[0010] Determine the energy consumption of the chiller in the target monitoring period according to the cooling effect and in combination with the time interval from when the cutting temperature rises to when the compressor speed changes.

[0011] Determine the regulation coefficient of the variable-frequency drive control system in the target monitoring period according to the energy consumption and in combination with the rising changes of the cutting temperature and the ambient temperature.

[0012] Regulate the operating speed of the compressor of the chiller according to the magnitude of the regulation coefficient and the compressor speed.

[0013] Furthermore, the specific steps for determining the demand degree of the chiller during the machining process of the numerically controlled machine tool in the monitoring period are as follows:

[0014] In the t-th monitoring period, obtain the information entropy of all extreme values in the cutting force at all times, take the mean value of the absolute values of the differences between all adjacent extreme values in the machine tool vibration data at all times as the first mean value, take the mean value of the time intervals between all adjacent extreme values in the machine tool vibration data at all times as the second mean value, and take the product of the ratio of the first mean value to the second mean value and the information entropy as the instantaneous state of the numerically controlled machine tool in the t-th monitoring period.

[0015] Obtain the mean square error between the cutting force and the cutting temperature at all times in the t-th monitoring period, and denote the ratio of the instantaneous state to the mean square error as the demand degree of the chiller during the machining process of the numerically controlled machine tool in the t-th monitoring period.

[0016] Furthermore, the specific steps for screening out the target monitoring period according to the magnitude of the demand degree are as follows:

[0017] In all monitoring periods, sort the monitoring periods in ascending order of the demand degree of the chiller during the machining process of the numerically controlled machine tool to obtain a monitoring period sequence.

[0018] In the monitoring period sequence, obtain the maximum value among the absolute values of the differences in the demand degree of the chiller during the machining process of the numerically controlled machine tool in all adjacent monitoring periods, and divide the monitoring period sequence into a left segment of the monitoring period sequence and a right segment of the monitoring period sequence from the middle of the adjacent monitoring periods corresponding to the maximum value.

[0019] Denote each monitoring period in the right segment of the monitoring period sequence as the target monitoring period.

[0020] Furthermore, the specific steps for determining the cooling effect of the chiller in the target monitoring period are as follows:

[0021] In the \(i\)th target monitoring period, the difference obtained by subtracting the cutting temperature at the \(j\)th moment from the cutting temperature at the \((j - 1)\)th moment is taken as the cutting temperature trend at the \(j\)th moment. The moment when the cutting temperature trend is positive is recorded as the cutting temperature rising moment. The absolute value of the difference between the inlet water temperature and the outlet water temperature of the chiller at the \(x\)th cutting temperature rising moment is calculated. The ratio of the cutting temperature trend at the \(x\)th cutting temperature rising moment to the absolute value of the difference is recorded as the first ratio at the \(x\)th cutting temperature rising moment. The reciprocal value of the average of the first ratios at all cutting temperature rising moments is taken as the cooling effect of the chiller in the \(i\)th target monitoring period.

[0022] Further, the specific steps for determining the energy consumption of the chiller in the target monitoring period are as follows:

[0023] The moment when the compressor speed changes each time is recorded as the speed adjustment moment;

[0024] Obtain the first response speed adjustment moment that appears after the \(x\)th cutting temperature rising moment in the \(i\)th target monitoring period;

[0025] Based on the time interval between the cutting temperature rising moment and the response speed adjustment moment, determine the response delay of the chiller control system in the \(i\)th target monitoring period;

[0026] The ratio of the response delay to the cooling effect of the chiller in the \(i\)th target monitoring period is taken as the energy consumption of the chiller in the \(i\)th target monitoring period.

[0027] Further, the specific steps for determining the response delay of the chiller control system in the \(i\)th target monitoring period based on the time interval between the cutting temperature rising moment and the response speed adjustment moment are as follows:

[0028] In the \(i\)th target monitoring period, obtain the time interval between the \(x\)th cutting temperature rising moment and the response speed adjustment moment corresponding to the \(x\)th cutting temperature rising moment as the response duration at the \(x\)th cutting temperature rising moment. The average of the response durations at all cutting temperature rising moments is taken as the response delay of the chiller control system in the \(i\)th target monitoring period.

[0029] Further, the specific steps for determining the regulation coefficient of the variable frequency drive control system in the target monitoring period are as follows:

[0030] In the i-th target monitoring period, the difference obtained by subtracting the ambient temperature at the y-th moment from the ambient temperature at the (y - 1)-th moment is taken as the ambient temperature trend at the y-th moment. The moments with a positive ambient temperature trend are recorded as ambient temperature rising moments. The average value of the ambient temperatures at all moments is calculated as the third average value. The absolute value of the difference between the ambient temperature trend and the cutting temperature trend at the g-th ambient temperature rising moment is calculated as the trend difference value at the g-th ambient temperature rising moment. The average value of the trend difference values at all ambient temperature rising moments is recorded as the fourth average value. The ratio of the third average value to the fourth average value is taken as the refrigeration loss of the chiller caused by the ambient temperature in the i-th target monitoring period;

[0031] Based on the refrigeration loss of the chiller caused by the ambient temperature and the energy consumption of the chiller in the i-th target monitoring period, determine the regulation coefficient of the variable frequency drive control system in the i-th target monitoring period.

[0032] Further, the step of determining the regulation coefficient of the variable frequency drive control system in the i-th target monitoring period based on the refrigeration loss of the chiller caused by the ambient temperature and the energy consumption of the chiller in the i-th target monitoring period includes the following specific steps:

[0033] The normalized value of the product of the refrigeration loss of the chiller caused by the ambient temperature and the energy consumption of the chiller in the i-th target monitoring period is taken as the regulation coefficient of the variable frequency drive control system in the i-th target monitoring period.

[0034] Further, the step of regulating the operating speed of the compressor of the chiller based on the regulation coefficient and the magnitude of the compressor speed includes the following specific steps:

[0035] If the current monitoring period is the target monitoring period, then calculate the product of the compressor speed at the current moment and the regulation coefficient of the variable frequency drive control system in the current monitoring period. And, if the regulation coefficient of the variable frequency drive control system in the current monitoring period is greater than the preset judgment threshold, then take the sum of the compressor speed at the current moment and the product as the regulated operating speed of the compressor. If the regulation coefficient of the variable frequency drive control system in the current monitoring period is less than or equal to the preset judgment threshold, then take the difference between the compressor speed at the current moment and the product as the regulated operating speed of the compressor.

[0036] The present invention also provides a chiller energy-saving control system, including a memory, a processor, and a computer program stored on the memory and executable on the processor. The processor executes the computer program stored in the memory to implement the steps of the foregoing chiller energy-saving control method.

[0037] The beneficial effects of the technical solution of the present invention are:

[0038] In the invention embodiment, the machining process of the numerical control machine tool is equally divided into several monitoring periods. According to the changes of the cutting force, cutting temperature and machine tool vibration data within the monitoring period, the demand degree of the chiller during the machining process of the numerical control machine tool within the monitoring period is determined to screen out the target monitoring period. Thus, by analyzing the machining state during the actual working process of the machining equipment and whether a large amount of heat is generated corresponding to the machining state, the target monitoring period when the chiller needs to operate is determined, ensuring the accuracy of the acquisition time that needs to be regulated. Furthermore, under the state of temperature rise during the machining process, the change of the outlet water temperature of the chiller is used to evaluate the cooling effect of the chiller. Combined with the response delay of the variable frequency control system to the temperature change, the energy consumption during the machining process of the chiller is explained. Then, through the temperature state of the environment where the chiller is located, the refrigeration loss under the environmental conditions is analyzed. Finally, the regulation coefficient for the energy-saving control of the chiller in the variable frequency control system is obtained. Thus, through the unstable analysis of the cooling effect and the heat transfer efficiency during the exchange process of cold and hot water, the regulation coefficient is obtained to ensure the refrigeration capacity of the chiller. Finally, the regulation coefficient is used to accurately regulate the operating speed of the compressor of the chiller. Thus far, the present invention achieves the purpose of energy-saving control of the chiller by obtaining the regulation coefficient for the energy-saving control of the chiller in the variable frequency control system and accurately regulating the operating speed of the chiller compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0040] Figure 1 It is a flowchart of the steps of an energy-saving control method for a chiller according to the present invention;

[0041] Figure 2 It is a schematic curve diagram of the change of machine tool vibration data with time. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following, in combination with the drawings and preferred embodiments, details the specific implementation manners, structures, features and effects of an energy-saving control method and system for a chiller according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs.

[0044] The following specifically describes the specific solutions of an energy-saving control method and system for a water chiller provided by the present invention in conjunction with the accompanying drawings.

[0045] Please refer to Figure 1 , which shows a flowchart of the steps of an energy-saving control method for a water chiller provided by an embodiment of the present invention. The method includes the following steps:

[0046] Step S001: During the machining process of a numerically controlled machine tool, obtain the cutting force, cutting temperature, machine tool vibration data, inlet water temperature, outlet water temperature, compressor speed, ambient temperature of the water chiller at each moment, and the moment when the compressor speed changes each time.

[0047] It should be noted that in industrial production, especially in fields such as mechanical manufacturing, electronic equipment production, and food processing, the water chiller, as a key cooling device, is responsible for maintaining the optimal operating temperature of the equipment and technological processes. When the main product of a large mechanical manufacturing factory is high-precision numerically controlled machine tools, a large amount of cutting heat will be generated during the machining process of such machine tools, resulting in an increase in the temperature of the cutting tool and the workpiece, thereby affecting the machining accuracy and the life of the cutting tool. The increase in the energy consumption of the water chiller is due to the fact that the existing energy-saving control system cannot achieve precise load regulation and lacks a certain degree of adaptability. Especially when the load changes violently, the equipment may experience overcooling or insufficient refrigeration because the traditional fixed-frequency and simple variable-frequency control systems lack flexibility and cannot respond to load changes in real time. Moreover, in the case of rapid load fluctuations, the response time of the existing system may be too long, resulting in the water chiller being unable to adjust in time, thereby causing energy waste.

[0048] During the machining process of a numerically controlled machine tool, collect the cutting force, cutting temperature, machine tool vibration data, inlet water temperature, outlet water temperature, compressor speed, ambient temperature of the water chiller at each moment, and the moment when the compressor speed changes each time.

[0049] It should be noted that: The acquisition frequency of the above data is once per second, and the following description is based on this example. In this embodiment, the min-max normalization method is used to standardize the data of each dimension, unifying the dimensions of data in different dimensions. This is a well-known technology. Piezoelectric sensors, temperature sensors, and vibration sensors installed on the machine tool are used to directly measure the cutting force, cutting temperature, and machine tool vibration data generated during the machining process of the CNC machine tool. Temperature sensors and rotational speed sensors at the inlet and outlet are used to collect the inlet temperature, outlet temperature, and compressor rotational speed of the chiller, so as to count the moments when the compressor rotational speed changes each time. A temperature sensor is used to collect the ambient temperature of the CNC machine tool. Among them, the schematic diagram of the curve of the machine tool vibration data changing with time is as Figure 2 shown, Figure 2 where the horizontal axis is time, the unit is second, and the vertical axis is the machine tool vibration data (vibration speed), the unit is millimeter per second.

[0050] It should be further noted that: In the chiller energy-saving control method and system, data acquisition is a key link to achieve precise control and optimize energy efficiency. The main data includes but is not limited to: temperature data (cooling water inlet temperature, outlet temperature, refrigerant evaporation temperature, and refrigerant condensation temperature), flow data (cooling chamber flow and refrigerant flow), pressure data (evaporator pressure and condenser pressure), and energy efficiency ratio data (real-time energy efficiency ratio and seasonal energy efficiency ratio). Select sensors that meet the environmental conditions and install the sensors at key positions of the chiller, including the evaporator, condenser, cooling water pipeline, and coolant pump, etc. Select a data collector (such as a PLC, embedded controller, or industrial computer) for signal acquisition to ensure that it can receive multiple input signals, and configure appropriate communication interfaces to transmit the sensor data to the data acquisition system. When the chiller starts working, start the data acquisition system and record the collected data in the database in real time for subsequent data analysis and processing.

[0051] Step S002: Divide the machining process of the CNC machine tool into several monitoring periods equally; according to the change situations of the cutting force, cutting temperature, and machine tool vibration data within the monitoring period, determine the demand degree of the chiller during the machining process of the CNC machine tool within the monitoring period.

[0052] It should be noted that: Analyze the actual machining state during the machining process of the CNC machine tool, and judge whether a large amount of cutting heat is generated during the machining process of the CNC machine tool through the change of the machining state. Frequent generation of cutting heat requires the chiller to respond quickly to ensure that the cooling effect matches the actual demand.

[0053] Preferably, in an embodiment of the present invention, the method for obtaining the demand degree of the chiller during the machining process of the CNC machine tool within the monitoring period includes:

[0054] A preset duration threshold S, where S is 20 minutes in this embodiment, and the following description is given by taking this as an example.

[0055] The machining process of the CNC machine tool is equally divided into several monitoring periods with a duration of S.

[0056] It should be noted that during the machining process of the CNC machine tool, starting from the first moment, every 20 minutes is used as a monitoring period. If the last monitoring period in which the current moment is located does not meet 20 minutes, it is also a monitoring period.

[0057] Within the t-th monitoring period, the extreme values of the cutting forces at all moments are obtained by using the first derivative method, and then the information entropy H of all the extreme values is obtained.

[0058] Within the t-th monitoring period, the extreme values of the machine tool vibration data at all moments are obtained by using the first derivative method. The absolute value of the difference and the time interval between any two adjacent extreme values are calculated. The average value of the absolute values of the differences between all adjacent extreme values is used as the first average value, and the average value of the time intervals between all adjacent extreme values is used as the second average value. The product of the ratio of the first average value to the second average value and the information entropy H is used as the state instantaneousness of the CNC machine tool within the t-th monitoring period.

[0059] It should be noted that both the first derivative method and the information entropy are well-known technologies, and the specific methods are not introduced here. Among them, the extreme values include maximum values and minimum values. The larger the information entropy, the more frequently the maximum and minimum values in the cutting force data change during the machining process, that is, different degrees of load changes occur during the machining process. The first average value reflects the average vibration amplitude during the machining process of the CNC machine tool, and the second average value reflects the vibration frequency during the machining process. Therefore, the larger the state instantaneousness, the more frequently the actual machining state changes instantaneously, that is, the higher the switching frequency of the working state of the chiller.

[0060] It should be noted that during the machining process of the CNC machine tool, the changes in the cutting force and the vibration amplitude can indicate a certain degree of frequent switching of the machining state. However, for the chiller, if the processing equipment does not generate corresponding temperature changes, there is no situation of untimely induction for the induction of the chiller.

[0061] The mean square error between the cutting forces and the cutting temperatures at all moments within the t-th monitoring period is obtained. The ratio of the state instantaneousness of the CNC machine tool within the t-th monitoring period to this mean square error is denoted as the demand degree of the chiller during the machining process of the CNC machine tool within the t-th monitoring period.

[0062] It should be noted that the mean square error is a well-known technology, and the specific method will not be introduced here. The smaller the mean square error, the more similar the changes in cutting force and cutting temperature during the monitoring period, that is, the closer the relationship between the temperature change and the actual load during the monitoring period. The larger the ratio of the state instantaneousness to the mean square error, the more heat is generated by the frequent switching of the machining mode during the machining process, and this heat needs to be transferred by the chiller, that is, the higher the demand for the chiller.

[0063] In the above manner, the demand for the chiller during the machining process of the CNC machine tool in each monitoring period is obtained.

[0064] Step S003: According to the magnitude of the demand, the target monitoring period is screened out; according to the rising change of the cutting temperature and the difference between the inlet water temperature and the outlet water temperature of the chiller during the target monitoring period, the cooling effect of the chiller in the target monitoring period is determined.

[0065] It should be noted that during the machining process of the CNC machine tool, due to the frequent switching of the machining mode during the machining process, a large amount of cutting heat may be generated, and thus it is urgent to use a chiller to transfer the generated heat. If the perception of the heat change during the operation of the chiller is delayed, it will cause an increase in the energy consumption of the chiller, and further cause the machining equipment to overheat or even be damaged. Therefore, in the case of frequent changes in the machining state of the CNC machine tool, the perception of the machining state by the chiller is analyzed to determine whether the response during the actual operation of the chiller meets the energy-saving control of the chiller.

[0066] Preferably, in an embodiment of the present invention, the method for obtaining the cooling effect of the chiller in the target monitoring period includes:

[0067] Among all the monitoring periods, the monitoring periods are sorted in ascending order of the demand for the chiller during the machining process of the CNC machine tool to obtain a monitoring period sequence.

[0068] In the monitoring period sequence, the absolute value of the difference in the demand for the chiller during the machining process of the CNC machine tool between any two adjacent monitoring periods is calculated, and the maximum value among the absolute values of the differences in the demand for the chiller during the machining process of the CNC machine tool in all adjacent monitoring periods is obtained. The monitoring period sequence is divided into a left segment and a right segment of the monitoring period sequence from the middle of the adjacent monitoring periods corresponding to the maximum value.

[0069] It should be noted that: in the monitoring period sequence, the demand degree increases from left to right. Therefore, the left segment of the monitoring period sequence can be considered as the monitoring time period with a relatively low demand degree for the chiller, and the switching frequency of the machining mode of the CNC machine tool is relatively low in this monitoring time period. The right segment is considered as the monitoring time period with a relatively high demand degree for the chiller, and the switching frequency of the machining mode of the CNC machine tool is relatively high in this monitoring time period.

[0070] Each monitoring period in the right segment of the monitoring period sequence is denoted as the target monitoring period.

[0071] In the i-th target monitoring period, the difference between the cutting temperature at the j-th moment and the cutting temperature at the (j - 1)-th moment is taken as the cutting temperature trend at the j-th moment.

[0072] It should be noted that: in this embodiment, the cutting temperature trend at the first moment in each target monitoring period is not analyzed. When the cutting temperature trend is a positive number, it indicates that the cutting temperature is showing an upward trend.

[0073] In the i-th target monitoring period, the moment when the cutting temperature trend is a positive number is denoted as the cutting temperature rising moment.

[0074] In the i-th target monitoring period, the absolute value of the difference between the inlet water temperature and the outlet water temperature of the chiller at the x-th cutting temperature rising moment is calculated, and the ratio of the cutting temperature trend at the x-th cutting temperature rising moment to this absolute value of the difference is denoted as the first ratio at the x-th cutting temperature rising moment. The reciprocal value of the mean value of all the first ratios at the cutting temperature rising moments is taken as the cooling effect of the chiller in the i-th target monitoring period.

[0075] It should be noted that: in this implementation, the reciprocal of the mean value is taken to perform an inverse proportion process on the mean value, and this is used as an example for description. The smaller the difference between the inlet water temperature and the outlet water temperature of the chiller, the less heat is dissipated under the current state of rising cutting temperature. Therefore, the greater the cutting temperature rise and the smaller the inlet and outlet water temperature difference, that is, the greater the first ratio, the worse the cooling effect during the operation of the chiller, which does not meet the expectation that when the cutting temperature rises, it means that more heat is generated during the cutting process and the cooling system needs to dissipate more heat.

[0076] Step S004: According to the cooling effect, in combination with the time interval from when the cutting temperature rises to when the compressor speed changes, determine the energy consumption of the chiller in the target monitoring period.

[0077] It should be noted that: Since there is a complementary relationship between the energy efficiency of the chiller and the cooling effect, a chiller with high energy efficiency can usually provide a more stable cooling effect, and a good cooling effect can help the chiller operate efficiently, reducing energy consumption. Modern chillers are equipped with a variable frequency drive system. When the system load increases and the temperature rises, the chiller can adjust the speed of the compressor, thereby increasing the refrigerant flow rate. Since the operation time of the control system generally triggers corresponding measures after the temperature rises, that is, the adjustment time of the compressor is generally after the moment of the rising temperature trend.

[0078] Preferably, in an embodiment of the present invention, the method for obtaining the energy consumption of the chiller during the target monitoring period includes:

[0079] Record the moment when the compressor speed changes each time as the speed adjustment moment.

[0080] Obtain the first speed adjustment moment that appears after the x-th cutting temperature rise moment in the i-th target monitoring period as the corresponding speed adjustment moment for the x-th cutting temperature rise moment.

[0081] It should be noted that: If there is no corresponding speed adjustment moment for a certain cutting temperature rise moment, this cutting temperature rise moment will not be analyzed.

[0082] In the i-th target monitoring period, obtain the time interval between the x-th cutting temperature rise moment and the corresponding speed adjustment moment of the x-th cutting temperature rise moment as the response duration of the x-th cutting temperature rise moment, and take the average value of the response durations of all cutting temperature rise moments as the response delay of the chiller control system in the i-th target monitoring period.

[0083] It should be noted that: When the cutting temperature rises during the machining process, the variable frequency control system of the chiller does not respond to this temperature change in a timely manner, which leads to an increase in the energy consumption of the chiller. That is, the larger the response duration, it means that when the cutting temperature rises each time, there is a large delay in the operation time of the control system, that is, the response delay of the control system is relatively high.

[0084] Take the ratio of the response delay of the chiller control system in the i-th target monitoring period to the cooling effect of the chiller in the i-th target monitoring period as the energy consumption of the chiller in the i-th target monitoring period.

[0085] It should be noted that: The larger the response delay, the greater the energy consumption, and the better the cooling effect, the smaller the energy consumption. Therefore, the larger the ratio, it means that in the current machining state of the CNC machine tool, the energy consumption of the chiller is relatively high. The reason is that the energy consumption of the chiller increases due to the lag in the response of the variable frequency control system to temperature changes.

[0086] Step S005: Determine the regulation coefficient of the variable frequency drive control system during the target monitoring period based on the energy consumption and in combination with the rising changes in the cutting temperature and the ambient temperature.

[0087] It should be noted that: In a high-temperature environment, the chiller needs to provide greater refrigeration capacity to maintain the normal operating temperature of the equipment or process. To cope with the higher load, the unit may need to operate for a longer time, resulting in increased energy consumption. During the process of evaluating the environmental conditions of the chiller in the current state, generally, the energy consumption of the chiller is greater at a higher ambient temperature because the compressor must overcome a higher exhaust temperature to achieve refrigeration, specifically manifested as an increase in the electricity required per unit of refrigeration capacity, thereby reducing the overall energy efficiency.

[0088] Preferably, in an embodiment of the present invention, the method for obtaining the regulation coefficient of the variable frequency drive control system during the target monitoring period includes:

[0089] In the i-th target monitoring period, take the difference between the ambient temperature at the y-th moment and the ambient temperature at the (y - 1)-th moment as the ambient temperature trend at the y-th moment.

[0090] It should be noted that: In this embodiment, the ambient temperature trend at the first moment in each target monitoring period is not analyzed. When the ambient temperature trend is positive, it indicates that the ambient temperature is showing an upward trend at this time.

[0091] In the i-th target monitoring period, mark the moment with a positive ambient temperature trend as the ambient temperature rising moment.

[0092] In the i-th target monitoring period, calculate the average value of the ambient temperatures at all moments as the third average value, calculate the absolute value of the difference between the ambient temperature trend and the cutting temperature trend at the g-th ambient temperature rising moment as the trend difference value at the g-th ambient temperature rising moment, calculate the average value of the trend difference values at all ambient temperature rising moments and denote it as the fourth average value, and take the ratio of the third average value to the fourth average value as the refrigeration loss of the chiller caused by the ambient temperature during the i-th target monitoring period.

[0093] It should be noted that: If the compressor of the chiller is in a high-temperature environment, then during the heat rejection process of the chiller, heat convection may be formed, thereby causing refrigeration loss of the chiller. That is, the smaller the trend difference value, the more it indicates that both the cutting temperature and the ambient temperature are in an upward trend, which may lead to the compressor being in a state of heat counteraction, resulting in refrigeration loss. Therefore, the larger the ratio, the more it indicates that when the heat generated by cutting during the processing rises, it may be in a high-temperature environment, thereby affecting the refrigeration capacity of the chiller and further expanding the refrigeration loss.

[0094] Normalize the product of the refrigeration loss of the chiller caused by the ambient temperature and the energy consumption of the chiller during the $i$-th target monitoring period, and use it as the regulation coefficient of the variable frequency drive control system during the $i$-th target monitoring period.

[0095] It should be noted that in this embodiment, the norm() linear normalization function is used to normalize the above product, and the data value is normalized to the interval [0, 1]. When the refrigeration loss and energy consumption are greater, the greater the regulation intensity of the operating speed of the compressor in the chiller is required.

[0096] Step S006: Regulate the operating speed of the compressor of the chiller according to the regulation coefficient and the magnitude of the compressor speed.

[0097] Preferably, in an embodiment of the present invention, the method for obtaining the regulated operating speed of the compressor includes:

[0098] Preset the judgment threshold to 0.5 and describe it by taking this as an example.

[0099] If the current monitoring period is the target monitoring period, calculate the product of the compressor speed at the current moment and the regulation coefficient of the variable frequency drive control system during the current monitoring period. And if the regulation coefficient of the variable frequency drive control system during the current monitoring period is greater than the preset judgment threshold, then use the sum of the compressor speed at the current moment and this product as the regulated operating speed of the compressor. If the regulation coefficient of the variable frequency drive control system during the current monitoring period is less than or equal to the preset judgment threshold, then use the difference between the compressor speed at the current moment and this product as the regulated operating speed of the compressor.

[0100] It should be noted that if the current monitoring period is not the target monitoring period, then the demand for the chiller during the machining process of the numerically controlled machine tool in the current monitoring period is relatively low, and there is no need to adjust the compressor speed. When the regulation coefficient is greater than the preset judgment threshold, it is considered that the machining of the numerically controlled machine tool is in a high-load state. At this time, the compressor should operate at a higher speed to meet the refrigeration demand, that is, increase the regulated operating speed of the compressor, so as to meet the refrigeration demand in the actual machining process. When the regulation coefficient is less than or equal to the preset judgment threshold, it is considered that the machining of the numerically controlled machine tool is in a low-load state. At this time, the compressor speed can be reduced through the regulation coefficient to reduce energy consumption, that is, reduce the regulated operating speed of the compressor. Thus, through methods such as real-time monitoring and variable frequency control, combined with the regulation coefficient of the obtained compressor operating speed, the energy-saving control of the chiller can be effectively carried out, and the energy consumption of the chiller can be effectively reduced.

[0101] The present invention also provides an energy-saving control system for a chiller, which includes a memory, a processor, and a computer program stored on the memory and executable on the processor. The processor executes the computer program stored in the memory to implement the steps of the aforementioned energy-saving control method for a chiller.

[0102] Thus, the present invention is completed.

[0103] In summary, in the embodiments of the present invention, the machining process of the CNC machine tool is equally divided into several monitoring periods. According to the changes in cutting force, cutting temperature, and machine tool vibration data within the monitoring period, the demand degree of the chiller during the machining process of the CNC machine tool within the monitoring period is determined to screen out the target monitoring period. According to the rising change of the cutting temperature and the difference between the inlet water temperature and the outlet water temperature of the chiller within the target monitoring period, the cooling effect of the chiller within the target monitoring period is determined. Combining the time interval from when the cutting temperature rises to when the compressor speed changes, the energy consumption of the chiller within the target monitoring period is determined. Then, combining the rising changes of the cutting temperature and the ambient temperature, the regulation coefficient of the variable-frequency drive control system within the target monitoring period is determined to regulate the operating speed of the compressor of the chiller. By obtaining the regulation coefficient for the energy-saving control of the chiller in the variable-frequency control system and regulating the operating speed of the compressor of the chiller, the present invention achieves the purpose of energy-saving control of the chiller.

[0104] The foregoing are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An energy-saving control method for a chiller, characterized in that The method includes the following steps: During the machining process of the numerically controlled machine tool, obtain the cutting force, cutting temperature, machine tool vibration data, inlet water temperature, outlet water temperature, compressor speed, ambient temperature of the chiller at each moment, and the moment when the compressor speed changes each time; Divide the machining process of the numerically controlled machine tool into several monitoring periods equally; according to the changes in the cutting force, cutting temperature, and machine tool vibration data within the monitoring period, determine the demand degree of the chiller during the machining process of the numerically controlled machine tool within the monitoring period; According to the magnitude of the demand degree, screen out the target monitoring period; according to the rising change of the cutting temperature and the difference between the inlet water temperature and the outlet water temperature of the chiller within the target monitoring period, determine the cooling effect of the chiller in the target monitoring period; According to the cooling effect, combined with the time interval from when the cutting temperature rises to when the compressor speed changes, determine the energy consumption of the chiller in the target monitoring period; According to the energy consumption, combined with the rising changes of the cutting temperature and the ambient temperature, determine the regulation coefficient of the variable frequency drive control system in the target monitoring period; According to the magnitude of the regulation coefficient and the compressor speed, regulate the operating speed of the compressor of the chiller.

2. The energy-saving control method for a water chiller according to claim 1, wherein, The specific steps included in determining the demand degree of the chiller during the machining process of the numerically controlled machine tool within the monitoring period are as follows: Within the t-th monitoring period, obtain the information entropy of all extreme values among the cutting forces at all moments, take the mean value of the absolute values of the differences between all adjacent extreme values in the machine tool vibration data at all moments as the first mean value, take the mean value of the time intervals between all adjacent extreme values in the machine tool vibration data at all moments as the second mean value, and take the product of the ratio of the first mean value to the second mean value and the information entropy as the state instantaneousness of the numerically controlled machine tool within the t-th monitoring period; Obtain the mean square error between the cutting force and the cutting temperature at all moments within the t-th monitoring period, and denote the ratio of the state instantaneousness to the mean square error as the demand degree of the chiller during the machining process of the numerically controlled machine tool within the t-th monitoring period.

3. The energy-saving control method for a chiller according to claim 1, wherein The specific steps included in screening out the target monitoring period according to the magnitude of the demand degree are as follows: Among all the monitoring periods, sort the monitoring periods in ascending order of the demand degree of the chiller during the machining process of the numerically controlled machine tool to obtain a monitoring period sequence; Within the monitoring period sequence, obtain the maximum value among the absolute values of the differences in the demand degrees of the chiller during the machining process of the numerically controlled machine tool between all adjacent monitoring periods, and divide the monitoring period sequence into a left segment of the monitoring period sequence and a right segment of the monitoring period sequence from the middle of the adjacent monitoring periods corresponding to the maximum value; Denote each monitoring period in the right segment of the monitoring period sequence as the target monitoring period.

4. The energy-saving control method of a water chiller according to claim 1, wherein The specific steps included in determining the cooling effect of the chiller in the target monitoring period are as follows: In the \(i\)th target monitoring period, the difference obtained by subtracting the cutting temperature at the \(j\)th moment from the cutting temperature at the \((j - 1)\)th moment is taken as the cutting temperature trend at the \(j\)th moment. The moment when the cutting temperature trend is positive is recorded as the cutting temperature rising moment. The absolute value of the difference between the inlet water temperature and the outlet water temperature of the chiller at the \(x\)th cutting temperature rising moment is calculated. The ratio of the cutting temperature trend at the \(x\)th cutting temperature rising moment to the absolute value of the difference is recorded as the first ratio at the \(x\)th cutting temperature rising moment. The reciprocal value of the average of all the first ratios at the cutting temperature rising moments is taken as the cooling effect of the chiller in the \(i\)th target monitoring period.

5. The energy-saving control method of a water chiller according to claim 1, characterized in that The specific steps for determining the energy consumption of the chiller in the target monitoring period are as follows: The moment when the compressor speed changes each time is recorded as the speed adjustment moment. Obtain the first response speed adjustment moment that appears after the \(x\)th cutting temperature rising moment in the \(i\)th target monitoring period. Based on the time interval between the cutting temperature rising moment and the response speed adjustment moment, determine the response delay of the chiller control system in the \(i\)th target monitoring period. Take the ratio of the response delay to the cooling effect of the chiller in the \(i\)th target monitoring period as the energy consumption of the chiller in the \(i\)th target monitoring period.

6. The energy-saving control method for a water chiller according to claim 5, characterized in that, The specific steps for determining the response delay of the chiller control system in the \(i\)th target monitoring period based on the time interval between the cutting temperature rising moment and the response speed adjustment moment are as follows: In the \(i\)th target monitoring period, obtain the time interval between the \(x\)th cutting temperature rising moment and the response speed adjustment moment corresponding to the \(x\)th cutting temperature rising moment as the response duration at the \(x\)th cutting temperature rising moment. Take the average of the response durations at all the cutting temperature rising moments as the response delay of the chiller control system in the \(i\)th target monitoring period.

7. The energy-saving control method of a chiller according to claim 4, characterized in that, The specific steps for determining the regulation coefficient of the variable frequency drive control system in the target monitoring period are as follows: In the \(i\)th target monitoring period, the difference obtained by subtracting the ambient temperature at the \(y\)th moment from the ambient temperature at the \((y - 1)\)th moment is taken as the ambient temperature trend at the \(y\)th moment. The moment when the ambient temperature trend is positive is recorded as the ambient temperature rising moment. Calculate the average of all the ambient temperatures as the third average. Calculate the absolute value of the difference between the ambient temperature trend and the cutting temperature trend at the \(g\)th ambient temperature rising moment as the trend difference value at the \(g\)th ambient temperature rising moment. Calculate the average of the trend difference values at all the ambient temperature rising moments and record it as the fourth average. Take the ratio of the third average to the fourth average as the refrigeration loss of the chiller caused by the ambient temperature in the \(i\)th target monitoring period. Based on the refrigeration loss of the chiller caused by the ambient temperature and the energy consumption of the chiller in the \(i\)th target monitoring period, determine the regulation coefficient of the variable frequency drive control system in the \(i\)th target monitoring period.

8. The energy-saving control method for a water chiller according to claim 7, characterized in that The specific steps for determining the regulation coefficient of the variable frequency drive control system in the \(i\)th target monitoring period based on the refrigeration loss of the chiller caused by the ambient temperature and the energy consumption of the chiller are as follows: Normalize the product of the refrigeration loss of the chiller caused by the ambient temperature in the i-th target monitoring period and the energy consumption of the chiller in the i-th target monitoring period, and use it as the regulation coefficient of the variable frequency drive control system in the i-th target monitoring period.

9. The energy-saving control method for a chiller according to claim 1, wherein According to the magnitude of the regulation coefficient and the compressor speed, regulating the operating speed of the compressor of the chiller includes the following specific steps: If the current monitoring period is the target monitoring period, calculate the product of the compressor speed at the current moment and the regulation coefficient of the variable frequency drive control system in the current monitoring period. And if the regulation coefficient of the variable frequency drive control system in the current monitoring period is greater than the preset judgment threshold, use the sum of the compressor speed at the current moment and the product as the regulated operating speed of the compressor; if the regulation coefficient of the variable frequency drive control system in the current monitoring period is less than or equal to the preset judgment threshold, use the difference between the compressor speed at the current moment and the product as the regulated operating speed of the compressor.

10. An energy-saving control system for a chiller, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the computer program is executed by the processor, it realizes the steps of an energy-saving control method for a chiller as described in any one of claims 1-9.

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