A method for intelligent power regulation and control of screw air compressor

Abstract

The present invention relates to the technical field of equipment or system control, and specifically to a method for intelligent power regulation and control of a screw air compressor. The method comprises: obtaining a current deviation window, obtaining a current deviation fluctuation intensity characterization value at the current control moment based on the deviation in the current deviation window, obtaining a historical deviation fluctuation intensity characterization value at the control moment adjacent to the current control moment, obtaining a differential item parameter adjustment factor based on the difference between the historical deviation fluctuation intensity characterization value and the current deviation fluctuation intensity characterization value and the standard deviation of the current deviation window, using the differential item parameter adjustment factor to adjust the differential item parameter at the control moment adjacent to the current control moment to obtain the differential item parameter at the current control moment; and using the differential item parameter at the current control moment to regulate the power of the screw air compressor at the current control moment. The present invention can also improve the control stability of the exhaust pressure of the screw air compressor.

Description

Technical Field

[0001] The present invention relates to the technical field of equipment or system regulation and control, and in particular to a method for intelligently regulating and controlling the power of a screw air compressor. Background Art

[0002] At present, in order to achieve energy consumption optimization, extend equipment life, reduce maintenance costs, and ensure production process stability, it is usually necessary to maintain the exhaust pressure of the screw air compressor at a set value, and the exhaust pressure of the screw air compressor is usually controlled by regulating the power of the screw air compressor. That is, the exhaust pressure of the screw air compressor is usually maintained at a set value by regulating the power of the screw air compressor. Therefore, regulating the power of the screw air compressor is crucial to the control stability of the exhaust pressure of the screw air compressor; and the PID controller is usually used to regulate the power of the screw air compressor in the prior art, but the PID controller is currently used to regulate the power of the screw air compressor. When controlling, fixed differential parameters are usually used to regulate the power of the screw air compressor. However, this method of regulating the power of the screw air compressor with fixed differential parameters will lead to poor control stability of the exhaust pressure of the screw air compressor, that is, this method of regulating the power of the screw air compressor with fixed differential parameters will cause the exhaust pressure of the screw air compressor to repeatedly overshoot and fall back and continue to oscillate in a small range. This repeated overshoot and fall back and continue to oscillate in a small range will have a negative impact on many aspects such as equipment life and production process stability. Therefore, how to regulate the power of the screw air compressor to improve the control stability of the exhaust pressure of the screw air compressor has become an urgent problem to be solved. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides a method for intelligently regulating and controlling the power of a screw air compressor. The technical solutions adopted are as follows:

[0004] One embodiment of the present invention provides a method for intelligently regulating and controlling the power of a screw air compressor, comprising the following steps:

[0005] Obtaining an actual pressure signal at the current control moment, wherein the actual pressure signal is composed of actual pressure data points, where the abscissa of the actual pressure data point is time and the ordinate is the actual pressure data of the screw air compressor;

[0006] Performing EMD decomposition on the actual pressure signal to obtain IMM components, and obtaining a current actual pressure data window at the current control moment according to the energy and period values ​​of the IMM components;

[0007] A current deviation window corresponding to the current actual pressure data window is obtained based on the difference between the target set pressure value and the actual pressure data in the current actual pressure data window, and a current deviation fluctuation intensity characterization value at the current control moment is obtained based on the deviation in the current deviation window; historical deviation fluctuation intensity characterization values ​​at control moments adjacent to the current control moment are obtained, and a differential item parameter adjustment factor is obtained based on the difference between the historical deviation fluctuation intensity characterization value and the current deviation fluctuation intensity characterization value and the standard deviation of the current deviation window, and the differential item parameter adjustment factor is used to adjust the differential item parameter at the control moments adjacent to the current control moment to obtain the differential item parameter at the current control moment;

[0008] The power of the screw air compressor at the current control moment is controlled by using the differential parameter at the current control moment.

[0009] Beneficial effect: The present invention first obtains the actual pressure signal at the current control moment; then performs EMD decomposition on the actual pressure signal to obtain IMM components, and obtains the current actual pressure data window at the current control moment based on the energy and period values ​​of the IMM components; then obtains the current deviation window corresponding to the current actual pressure data window based on the difference between the target set pressure value and the actual pressure data in the current actual pressure data window, and obtains the current deviation fluctuation intensity characterization value at the current control moment based on the deviation in the current deviation window; obtains the historical deviation fluctuation intensity characterization value at the adjacent control moments of the current control moment, obtains the differential item parameter adjustment factor based on the difference between the historical deviation fluctuation intensity characterization value and the current deviation fluctuation intensity characterization value and the standard deviation of the current deviation window, and uses the differential item parameter adjustment factor to adjust the differential item parameters at the adjacent control moments of the current control moment to obtain the differential item parameters at the current control moment; finally, uses the differential item parameters at the current control moment to control the power of the screw air compressor at the current control moment. Moreover, the present invention dynamically adjusts the differential parameters of the PID controller and regulates the power of the screw air compressor based on the parameters of the dynamically adjusted PID controller, thereby reducing the occurrence of continuous small oscillations such as repeated overshoot and fall of the exhaust pressure of the screw air compressor, thereby improving the control stability of the exhaust pressure of the screw air compressor, that is, improving the control stability of the screw air compressor system. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0011] Figure 1 This is a flow chart of a method for intelligent power regulation and control of a screw air compressor according to the present invention. DETAILED DESCRIPTION

[0012] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field fall within the scope of protection of the embodiments of the present invention.

[0013] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0014] This embodiment provides a method for intelligently regulating and controlling the power of a screw air compressor, which is described in detail as follows:

[0015] like Figure 1 As shown, the screw air compressor power intelligent regulation control method includes the following steps:

[0016] Step S001: Acquire the actual pressure signal at the current control moment.

[0017] This embodiment mainly improves the control stability of the exhaust pressure of the screw air compressor by adaptively adjusting the differential parameter of the PID controller used when regulating the power of the screw air compressor. That is, this embodiment mainly avoids the occurrence of repeated small fluctuations in the exhaust pressure of the screw air compressor, such as repeated overshoot and fall, or avoids the occurrence of small fluctuations in the exhaust pressure of the screw air compressor around the set value, by adaptively adjusting the differential parameter of the PID controller used when regulating the power of the screw air compressor. In addition, the screw air compressor is usually a core component, which together with other auxiliary equipment constitutes a screw air compressor system, thereby providing stable compressed air pressure for production lines, pneumatic equipment, etc. The purpose of regulating the power of the screw air compressor is also to control the exhaust pressure of the screw air compressor system. Therefore, the control input is pressure data, which is then output by the PID controller as an inverter frequency control instruction. That is, the purpose of regulating the power of the screw air compressor is to control the exhaust pressure of the screw air compressor.

[0018] This embodiment will next be described by taking the power regulation process of any screw air compressor as an example, that is, the screw air compressor that appears later in this embodiment is the same screw air compressor, and since the purpose of regulating the power of the screw air compressor is to control the exhaust pressure of the screw air compressor, the differential parameter of the PID controller used in the subsequent power regulation of the screw air compressor is adaptively adjusted, and reference to the exhaust pressure is required. Therefore, this embodiment then needs to first obtain the actual pressure signal at the current regulation moment. The actual pressure signal at the current regulation moment is the basis for subsequently obtaining the differential parameter at the current regulation moment. Then the specific process of the actual pressure signal at the current regulation moment is:

[0019] At each sampling moment in the time period from the start of operation of the screw air compressor to the current control moment, the exhaust pressure data of the screw air compressor collected by the industrial pressure sensor is obtained, and then the exhaust pressure data collected in the time period from the start of operation of the screw air compressor to the current control moment is denoised using a filtering algorithm, and the denoised data is recorded as the actual pressure data of the screw air compressor at the corresponding sampling moment, that is, for any sampling moment, the actual pressure data of the screw air compressor at the sampling moment is the data obtained after denoising the exhaust pressure data of the screw air compressor collected by the industrial pressure sensor at the sampling moment; then a two-dimensional space is constructed, and the two-dimensional space The horizontal axis represents time, and the vertical axis represents actual pressure data. Then, the actual pressure data of all screw air compressors obtained in the time period from the start of operation to the current control moment and the acquisition time corresponding to the actual pressure data are mapped into the two-dimensional space to obtain the actual pressure data points in the two-dimensional space. Then, all the actual pressure data points in the two-dimensional space are connected in order of acquisition time, and the signal curve obtained after the connection is completed is recorded as the actual pressure signal at the current control moment; and if the horizontal coordinate value of any actual pressure data point is t0, then the vertical coordinate value of the actual pressure data point is the actual pressure data of the screw air compressor at the acquisition time t0.

[0020] In this embodiment, the frequency at which the industrial pressure sensor collects exhaust pressure data is set based on experience. Generally, the frequency is set between 5Hz and 10Hz. If intelligent frequency conversion is used, the frequency is typically set between 10Hz and 20Hz. However, the exhaust pressure data collection time of the screw compressor is required to be synchronized with the power adjustment time of the screw compressor. Furthermore, since the original output signal of the industrial pressure sensor is not essentially a pressure unit, but rather a raw coded value that corresponds linearly to the pressure, the exhaust pressure data of the screw compressor collected in this embodiment is data after range conversion. Furthermore, the industrial pressure sensor performs a limiting operation when collecting the exhaust pressure of the screw compressor. The limiting and range conversion of the sensor in this embodiment are both well known. In this embodiment, the implementer can select a filtering algorithm to denoise the collected exhaust pressure data based on actual conditions. For example, in this embodiment, a low-pass filter can be selected.

[0021] Therefore, this embodiment obtains the actual pressure signal at the current control moment through the above process.

[0022] Step S002 : performing EMD decomposition on the actual pressure signal to obtain IMM components, and obtaining a current actual pressure data window at the current control moment according to the energy and period values ​​of the IMM components.

[0023] Currently, when using PID algorithm to control the power of screw air compressor, fixed differential parameters are usually used to control the power of screw air compressor. However, this method of using fixed differential parameters to control the power of screw air compressor will lead to poor control stability of the exhaust pressure of screw air compressor. That is, this method of using fixed differential parameters to control the power of screw air compressor will lead to continuous small oscillation of exhaust pressure of screw air compressor with repeated overshoot and fall. For example, if the fixed differential parameters are used to control the power of screw air compressor, the exhaust pressure of screw air compressor will be greatly improved. If the fixed differential parameter is relatively small, the deviation change will be insufficiently suppressed, resulting in continuous overshoot. If the fixed differential parameter is relatively large, the adjustment amount will be excessively offset, causing the exhaust pressure of the screw air compressor to oscillate repeatedly around the set value, making it difficult to maintain at the set value. This repeated overshoot and fall-back phenomenon of continuous small oscillations will have a negative impact on equipment life, production process stability and other aspects, such as accelerating equipment loss and failure risks, causing energy efficiency degradation and energy waste, and damaging production process stability.

[0024] In order to improve the control stability of the exhaust pressure of the screw air compressor, that is, in order to avoid the occurrence of repeated small oscillations of the exhaust pressure of the screw air compressor as much as possible, the present embodiment will subsequently adjust the differential parameters adaptively according to the analysis of the deviation fluctuations, and then adjust the power of the screw air compressor based on the differential parameters obtained by the adaptive adjustment, so as to achieve the purpose of controlling the exhaust pressure of the screw air compressor. However, since the exhaust pressure data has the characteristics of nonlinearity, hysteresis and time-varying, the subsequent analysis cannot be based on a single data, but multiple data must be selected. However, in order to make the deviation fluctuations analyzed later more realistic, In order to be practical and effective, this embodiment requires that the selected actual pressure data length can include a complete overshoot to fallback process as much as possible. The complete overshoot to fallback process refers to a complete response from an overshoot to a fallback to the set value. Therefore, this embodiment needs to analyze the periodic characteristics of the actual pressure signal at the current control moment, and then determine the data length used for subsequent adjustment of the differential item parameters based on the obtained periodic characteristics. That is to say, the current actual pressure data window corresponding to the current control moment is determined based on the obtained periodic characteristics. However, due to the nonlinearity, hysteresis and disturbance characteristics of the screw air compressor system, the actual pressure data obtained is often in a non-stationary state. Therefore, directly analyzing the actual pressure signal is not a good choice. It is difficult to extract the true periodic characteristics of the pressure signal. In order to ensure the reliability of the periodic characteristics of the actual pressure signal being analyzed, this embodiment will first perform EMD decomposition on the actual pressure signal at the current control moment, output all the IMM components obtained by decomposition, and then calculate the energy and periodic value of each IMM component. The energy of any IMM component is the sum of the squares of the ordinate values ​​of all sampling points on the IMM component, and the time of the abscissa value of any sampling point on the IMM component is the acquisition moment. EMD can decompose the signal into IMF components with local characteristics. There are relatively regular periodic changes in the IMF components. In addition, the periodic value of any IMM component refers to the intersection of the IMM component and the zero line. The zero line refers to the horizontal axis in the two-dimensional space, which is also the time axis. That is, for any IMM component, first obtain the intersection of the IMM component and the zero line, and arrange all the intersections of the IMM component and the zero line in chronological order to obtain the intersection sequence corresponding to the IMM component, obtain the average value of the time intervals between all adjacent intersections in the intersection sequence, and record it as the period value of the IMM component. The calculation method of the period value of the above-mentioned IMM component belongs to the average period method. As other implementation methods, other well-known methods can also be used to obtain the period value of the IMM component. For example, the implementer can choose to use the energy spectrum density-period analysis method to calculate the period of the IMM component.

[0025] After obtaining the energy and period value of each IMM component, the current actual pressure data window at the current control moment is obtained according to the energy and period value of each IMM component. The specific process is as follows:

[0026] First, all the IMM components obtained by decomposition are sorted according to the energy size, and the sorted sequence is recorded as the IMM component sequence; then the sequence to be analyzed is obtained according to the position and energy of the IMM components in the IMM component sequence; and the acquisition process of the sequence to be analyzed is: obtain the cumulative sum of the energies of all IMM components in the IMM component sequence, and record it as the first total energy, judge whether the ratio of the cumulative sum of the energies of the first N IMM components in the IMM component sequence to the first total energy is greater than the preset proportion threshold, and whether the ratio of the cumulative sum of the energies of the first N-1 IMM components in the IMM component sequence to the first total energy is not greater than the preset proportion threshold. If both are true, then the new sequence composed of the first N IMM components in the IMM component sequence is recorded as the sequence to be analyzed, that is, when the cumulative sum of the energies of the first N IMM components in the IMM component sequence is greater than the first total energy, ... When the ratio of the total energy is greater than the preset proportion threshold, and the ratio of the sum of the energies of the first N-1 IMM components in the IMM component sequence to the first total energy is not greater than the preset proportion threshold, the new sequence composed of the first N IMM components in the IMM component sequence is the sequence to be analyzed, and N is greater than 1; and in specific applications, the implementer needs to set the preset proportion threshold according to actual conditions or relevant experience. For example, in this embodiment, the preset proportion threshold can be set to 0.8, but it is required that it should not be too small or too large. If it is too small, key mid- and low-frequency components will be omitted, and the signal characterization will be incomplete. If it is too large, redundancy of high-order IMF will be introduced. In addition, the purpose of obtaining the sequence to be analyzed based on the preset proportion threshold in this embodiment is to improve the reliability of the target period value obtained subsequently, so that the obtained target period value can be closer to the energy concentration part of the actual pressure signal at the current control moment.

[0027] After obtaining the sequence to be analyzed, the weight factors of each IMM component in the sequence to be analyzed are obtained. For any IMM component in the sequence to be analyzed, this embodiment uses the ratio of the energy of the IMM component to the second total energy as the weight factor of the IMM component. The second total energy is the cumulative sum of the energies of all IMM components in the sequence to be analyzed. In addition, since in the EMD decomposition process, as the IMF order increases, the proportion of noise and short-term disturbances in the component components increases. Therefore, the reference value of the period value of the IMM component with a higher IMF order is smaller. Therefore, this embodiment makes the weight factor of the IMM component with a larger energy larger, that is, the period value of the IMM component with a larger energy has a greater contribution to the subsequent determination of the target period value at the current control moment. Therefore, after obtaining the weight factors of each IMM component in the sequence to be analyzed, this embodiment calculates the product of the weight factors of each IMM component in the sequence to be analyzed and the period value of the corresponding IMM component, and uses it as the weighted period value of the corresponding IMM component. The cumulative sum of the weighted period values ​​of all IMM components in the sequence to be analyzed is calculated and recorded as the target period value at the current control moment. The specific calculation formula of the target period value at the current control moment is: , where N is the total number of IMM components in the sequence to be analyzed, is the weight factor of the nth IMM component in the sequence to be analyzed, is the period value of the nth IMM component in the sequence to be analyzed, and the target period value at the current control moment is the length of the current actual pressure data window corresponding to the current control moment; then, all actual pressure data whose acquisition time is within the interval [TL, T] are obtained, and a window constructed by all actual pressure data whose acquisition time is within the interval [TL, T] is used as the current actual pressure data window at the current control moment, where T is the current control moment and L is the target period value at the current control moment; and this method of dynamically obtaining the current actual pressure data window in this embodiment can provide a reliable basis for subsequent analysis of the current oscillation trend.

[0028] Therefore, this embodiment obtains the current actual pressure data window corresponding to the current control moment through the above process.

[0029] Step S003: obtain the current deviation window corresponding to the current actual pressure data window according to the difference between the target set pressure value and the actual pressure data in the current actual pressure data window, and obtain the current deviation fluctuation intensity characterization value at the current control moment according to the deviation in the current deviation window; obtain the historical deviation fluctuation intensity characterization value at the adjacent control moments of the current control moment, and obtain the differential item parameter adjustment factor according to the difference between the historical deviation fluctuation intensity characterization value and the current deviation fluctuation intensity characterization value and the standard deviation of the current deviation window, and use the differential item parameter adjustment factor to adjust the differential item parameter at the adjacent control moments of the current control moment to obtain the differential item parameter at the current control moment.

[0030] This embodiment will then determine the differential parameter at the current control moment based on the data window obtained above. The specific process is as follows:

[0031] First, the set pressure value of the screw air compressor is obtained and recorded as the target set pressure value, and the set pressure value of the screw air compressor refers to the target exhaust pressure pre-configured by the user on the screw air compressor control system; then, based on the difference between the target set pressure value and the actual pressure data in the current actual pressure data window, the current deviation window corresponding to the current actual pressure data window is obtained. The current deviation window is the key to subsequently obtaining the differential item parameter adjustment direction characterization value and the differential item parameter adjustment amplitude, and the ath deviation in the current deviation window corresponding to the current actual pressure data window is the result of subtracting the ath actual pressure data in the current actual pressure data window from the target set pressure value, that is, the ath deviation in the current deviation window is the deviation of the ath actual pressure data in the current actual pressure data window. The calculation process of the deviation of the actual pressure data in this embodiment is well known.

[0032] After obtaining the current deviation window corresponding to the current actual pressure data window of the current control moment, the adjacent control moment of the current control moment is obtained. The adjacent control moment of the current control moment refers to the control moment adjacent to the current control moment and located before the current control moment in time. Then the historical actual pressure data window of the adjacent control moment of the current control moment is obtained. According to the difference between the target set pressure value and the actual pressure data in the historical actual pressure data window of the adjacent control moment of the current control moment, the historical deviation window corresponding to the historical actual pressure data window of the adjacent control moment of the current control moment is obtained; and the method for obtaining the historical actual pressure data window of the adjacent control moment of the current control moment and the historical deviation window corresponding to the historical actual pressure data window of the adjacent control moment of the current control moment is the same as the method for obtaining the current actual pressure data window of the current control moment and the current deviation window corresponding to the current actual pressure data window of the current control moment, so they are not described in detail.

[0033] After obtaining the current deviation window corresponding to the current actual pressure data window of the current control moment and the historical deviation window corresponding to the historical actual pressure data window of the adjacent control moment of the current control moment, the current deviation fluctuation intensity characterization value at the current control moment is obtained according to the deviation in the current deviation window corresponding to the current actual pressure data window of the current control moment, and the historical deviation fluctuation intensity characterization value at the adjacent control moment of the current control moment is obtained according to the deviation in the historical deviation window corresponding to the historical actual pressure data window of the adjacent control moment of the current control moment. The deviation fluctuation intensity characterization value at any control moment is the deviation fluctuation of the actual pressure data in the actual pressure data window representing the corresponding control moment, or the deviation fluctuation in the deviation window corresponding to the actual pressure data window representing the corresponding control moment.

[0034] Furthermore, since the method for obtaining the deviation fluctuation intensity characterization value at any control moment is the same, that is, the method for obtaining the current deviation fluctuation intensity characterization value at the current control moment is the same as the method for obtaining the historical deviation fluctuation intensity characterization value at the adjacent control moments of the current control moment, then for ease of understanding, this embodiment will take the process of obtaining the current deviation fluctuation intensity characterization value at the current control moment as an example to describe, and the specific process of obtaining the current deviation fluctuation intensity characterization value at the current control moment is: first, obtain the cumulative sum of all the absolute values ​​of the deviations in the current deviation window, and record it as the comprehensive deviation, then calculate the ratio of each absolute value of the deviation in the current deviation window to the comprehensive deviation, and record it as the weight factor of the corresponding deviation, and then obtain the square value of each deviation in the current deviation window; and since larger deviations can better characterize the intensified fluctuation or unstable response of the screw air compressor, this embodiment is In order to better reflect the severity of the deviation fluctuation, when calculating the deviation fluctuation intensity at the control moment, the larger the deviation, the more it can dominate the final result. That is, when calculating the deviation fluctuation intensity at the control moment, in order to make the calculated result better reflect the deviation fluctuation intensity at the corresponding control moment, not only the square of the deviation is used to amplify the impact of the larger deviation on the result, but also the participation or contribution of the larger deviation to the result is greater; then based on the above analysis, it can be seen that according to the square value of each deviation in the current deviation window and the weight factor of the corresponding deviation, the weighted deviation of each deviation in the current deviation window is obtained, and then the cumulative sum of the weighted deviations of all deviations in the current deviation window is calculated, and used as the current deviation fluctuation intensity representation value corresponding to the current control moment; and for any deviation in the current deviation window, the weighted deviation of the deviation refers to the product of the square value of the deviation and the weight factor of the deviation.

[0035] After obtaining the current deviation fluctuation intensity representation value at the current control moment and the historical deviation fluctuation intensity representation value at the control moments adjacent to the current control moment, the differential item parameter adjustment factor at the current control moment is obtained based on the difference between the historical deviation fluctuation intensity representation value at the control moments adjacent to the current control moment and the current deviation fluctuation intensity representation value and the standard deviation of the current deviation window; and the differential item parameter adjustment factor is the key to determining the differential item parameter at the current control moment, so the specific process of obtaining the differential item parameter adjustment factor at the current control moment is:

[0036] First, calculate the result of subtracting the historical deviation fluctuation intensity characterization value from the current deviation fluctuation intensity characterization value, and record it as the deviation fluctuation change characterization value at the current control moment. Then determine whether the deviation fluctuation change characterization value at the current control moment is equal to the preset judgment threshold. If it is equal, it indicates that the deviation fluctuation intensity trend at the current control moment is stable. At this time, the differential item parameters of the PID controller do not need to be adjusted, and the control stability of the exhaust pressure of the screw air compressor can also be guaranteed. Therefore, when the deviation fluctuation change characterization value is equal to the preset judgment threshold, there is no need to calculate the differential item parameter adjustment factor at the current control moment. The constant 1 can be directly used as the differential item parameter adjustment factor at the current control moment. That is, when the deviation fluctuation change characterization value is equal to the preset judgment threshold, there is no need to calculate the differential item parameter adjustment direction characterization value and the differential item parameter adjustment amplitude.

[0037] However, when it is determined that the deviation fluctuation change characterization value at the current control moment is not equal to the preset judgment threshold, it indicates that the deviation fluctuation intensity at the previous control moment has an increasing or decreasing trend. At this time, the differential item parameter of the PID controller needs to be adjusted to ensure the control stability of the exhaust pressure of the screw air compressor. Therefore, when it is determined that the deviation fluctuation change characterization value at the current control moment is not equal to the preset judgment threshold, the differential item parameter adjustment direction characterization value at the current control moment is first obtained based on the deviation fluctuation change characterization value and the preset judgment threshold. The differential item parameter adjustment direction characterization value can control the adjustment direction, that is, the differential item parameter adjustment direction characterization value can control whether to increase or decrease. Then, based on the absolute value of the deviation fluctuation change characterization value and the standard deviation of the current deviation window, the differential item parameter adjustment amplitude at the current control moment is obtained. Finally, based on the differential item parameter adjustment direction characterization value at the current control moment and the differential item parameter adjustment amplitude at the current control moment, the differential item parameter adjustment factor at the current control moment is obtained. In addition, since the change of data at one moment relative to another moment is usually judged based on 0, the preset judgment threshold is set to 0 in this embodiment.

[0038] In this embodiment, the specific process of obtaining the differential parameter adjustment direction representation value at the current control moment according to the deviation fluctuation change representation value at the current control moment and the preset judgment threshold is as follows:

[0039] Determine whether the deviation fluctuation change characterization value is greater than the preset judgment threshold. If so, it indicates that the current control moment is relative to the adjacent control moment of the current control moment, that is, the current control moment is relative to the previous control moment of the current control moment. The deviation fluctuation intensity at the current control moment has an increasing trend, which also indicates that the screw air compressor system is in a drastic adjustment stage. At this time, if the differential parameter of the PID controller is relatively small, the controller will be insensitive to such changes, then it may not be able to suppress the upcoming overshoot or rebound in time, thereby exacerbating the oscillation. Therefore, the differential parameter should be increased to enhance its inhibitory effect. That is, in order to make the screw air compressor system more sensitive to capture the deviation change trend, the differential parameter of the PID controller should be increased to strengthen the reflection of the deviation change. Therefore, when the deviation fluctuation change characterization value is greater than When the judgment threshold is preset, the constant 1 is used as the characterization value of the differential parameter adjustment direction at the current control moment; if the deviation fluctuation change characterization value is judged to be less than the preset judgment threshold, it indicates that the deviation fluctuation intensity at the current control moment is relative to the previous control moment. There is a trend of decreasing, then the differential parameter of the PID controller should be reduced to prevent the controller from overreacting, so as to ensure that the screw air compressor system maintains a stable working state, that is, when the deviation fluctuation weakens, it means that the screw air compressor system is tending to be stable. At this time, the larger differential parameter of the PID controller may cause a lonely reaction, which will cause the system to adjust and oscillate frequently. The differential parameter should be lowered. Therefore, when the deviation fluctuation change characterization value is less than the preset judgment threshold, negative 1 is used as the characterization value of the differential parameter adjustment direction at the current control moment.

[0040] In this embodiment, the specific process of obtaining the differential parameter adjustment amplitude at the current control moment based on the absolute value of the deviation fluctuation change characterization value and the standard deviation of the current deviation window is as follows: first, the absolute value of the deviation fluctuation change characterization value is normalized using the hyperbolic tangent function, and the normalized result is recorded as the normalized deviation fluctuation change characterization value, the standard deviation of the current deviation window is obtained, and the standard deviation of the current deviation window is normalized using the hyperbolic tangent function, and the normalized result is recorded as the normalized deviation standard deviation, and the mean of the normalized deviation fluctuation change characterization value and the normalized deviation standard deviation is calculated and used as the differential parameter adjustment amplitude at the current control moment. The specific formula for calculating the differential parameter adjustment amplitude at the current control moment is:

[0041]

[0042] Where W is the adjustment amplitude of the differential parameter at the current control moment, tanh() is the hyperbolic tangent function, and D is the deviation fluctuation change characterization value. Is the standard deviation of the current deviation window; and the greater the absolute value of the deviation fluctuation characterization value, it indicates that the screw air compressor system at the current control moment is in a rapid change period, or the current control moment is relative to the previous control moment of the current control moment. The greater the degree of change in the exhaust pressure of the screw air compressor at the current control moment, then in order to improve the control stability of the exhaust pressure of the screw air compressor, the PID controller needs to respond more actively to this change, that is, the differential parameter of the PID controller should be adjusted more significantly at this time; and the larger the standard deviation of the current deviation window, the less concentrated the deviation distribution in the current deviation window, the more severe the deviation fluctuation, and the smaller the deviation in the window. The greater the degree of difference dispersion, the greater the probability that the screw air compressor system is affected by the superposition of load changes or control output delays, and the more unstable the screw air compressor system is, then the differential parameters of the PID controller should be adjusted more significantly to suppress overshoot and continuous oscillation; it can be seen that when the absolute value of the deviation fluctuation change characterization value is larger and the standard deviation of the current deviation window is larger, that is, the larger the adjustment range of the differential parameters at the current control moment, it indicates that relative to the differential parameters of the PID controller at the previous control moment, the adjustment range of the differential parameters of the PID controller is larger at this time, and vice versa.

[0043] In this embodiment, according to the differential parameter adjustment direction representation value at the current control moment and the differential parameter adjustment amplitude at the previous control moment, the specific formula for obtaining the differential parameter adjustment factor at the current control moment is:

[0044]

[0045] Among them, Q is the differential parameter adjustment factor at the current control moment, c is the preset adjustment control coefficient, F is the differential parameter adjustment direction representation value at the current control moment, and W is the differential parameter adjustment amplitude at the current control moment; and when the value of F is 1, and the larger the value of W is, the greater the increase in the differential parameter at the previous control moment of the current control moment, and the previous control moment of the current control moment is the adjacent control moment of the current control moment; when the value of F is 1, and the smaller the value of W is, the less the increase in the differential parameter at the previous control moment of the current control moment; when the value of F is -1, and the larger the value of W, the greater the degree of reduction of the differential item parameter at the previous control moment of the current control moment; when the value of F is -1, and the smaller the value of W, the less the degree of reduction of the differential item parameter at the previous control moment of the current control moment; in addition, in this embodiment, the implementer needs to set the preset adjustment control coefficient according to the maximum degree of increase or decrease of the differential item parameter. For example, this embodiment requires that the maximum degree of increase or decrease of the differential item parameter does not exceed the value of the differential item parameter at the previous control moment of the current control moment, so this embodiment sets the preset adjustment control coefficient to 1.

[0046] After obtaining the differential parameter adjustment factor at the current control moment, the differential parameter at the adjacent control moment of the current control moment is obtained, that is, the differential parameter of the PID controller at the previous control moment of the current control moment, and then the differential parameter adjustment factor at the current control moment is used to adjust the differential parameter at the adjacent control moment of the current control moment, and the differential parameter obtained after adjustment is used as the differential parameter at the current control moment; and the differential parameter at the previous control moment is the product of the differential parameter at the adjacent control moment of the current control moment and the differential parameter adjustment factor at the current control moment, that is, the differential parameter at the current control moment is ,in, is the differential parameter at the adjacent control moment of the current control moment.

[0047] Therefore, this embodiment obtains the differential term parameters at the current control moment through the above process.

[0048] Step S004: Regulate the power of the screw air compressor at the current regulation moment by using the differential parameter at the current regulation moment.

[0049] Since under normal circumstances, when the differential item parameters are adjusted, the proportional item parameters and the integral item parameters also need to be adjusted synchronously, so it is necessary to synchronously adjust the proportional item parameters and the integral item parameters at the adjacent control moments of the current control moment according to the proportional item parameters, the integral item parameters, the differential item parameters at the adjacent control moments of the current control moment and the differential item parameters at the current control moment to obtain the proportional item parameters and the integral item parameters at the current control moment. When adjusting the differential item parameters, the process of synchronously adjusting the proportional item parameters and the integral item parameters is well known, that is, when adjusting the differential item parameters, the integral item parameters at the current control moment are usually obtained according to engineering experience requirements. For example, if engineering experience requires that the integral item parameter is between 4 times the differential item parameter and 8 times the differential item parameter, then the integral item parameter at the current control moment is between 4×Td and 8×Td, and Td is the differential item parameter at the current control moment. When adjusting the differential item parameters, it is generally based on the formula The calculated result is used as the proportional term parameter at the current control moment, and when calculating the proportional term parameter at the current control moment, the formula is the proportional term parameter at the adjacent control time of the current control time, is the differential parameter at the adjacent control moment of the current control moment, is the differential parameter obtained at the current control moment, is the empirical buffer coefficient, It is generally set to between 0.8 and 0.9; the proportional term parameter, the integral term parameter, and the differential term parameter in this embodiment are three parameters of the PID controller.

[0050] After obtaining the differential, proportional, and integral parameters of the PID controller at the current control moment, the power of the screw air compressor at the current control moment is controlled based on the differential, proportional, and integral parameters of the PID controller at the current control moment. Given the three parameters of the PID controller, the specific process of controlling the power of the screw air compressor is a well-known technique. This embodiment dynamically adjusts the differential parameters of the PID controller and controls the power of the screw air compressor based on the dynamically adjusted parameters of the PID controller. This reduces or suppresses the occurrence of small, continuous oscillations in the exhaust pressure of the screw air compressor caused by inverter adjustment delays, cumulative effects of delays after gas compression, and the like, thereby improving the control stability of the exhaust pressure of the screw air compressor.

[0051] To summarize, this embodiment first obtains the actual pressure signal at the current control moment; then performs EMD decomposition on the actual pressure signal to obtain the IMM component, and obtains the current actual pressure data window at the current control moment based on the energy and period value of the IMM component; then obtains the current deviation window corresponding to the current actual pressure data window based on the difference between the target set pressure value and the actual pressure data in the current actual pressure data window, and obtains the current deviation fluctuation intensity characterization value at the current control moment based on the deviation in the current deviation window; obtains the historical deviation fluctuation intensity characterization value at the adjacent control moments of the current control moment, obtains the differential item parameter adjustment factor based on the difference between the historical deviation fluctuation intensity characterization value and the current deviation fluctuation intensity characterization value and the standard deviation of the current deviation window, and uses the differential item parameter adjustment factor to adjust the differential item parameters at the adjacent control moments of the current control moment to obtain the differential item parameters at the current control moment; finally, uses the differential item parameters at the current control moment to control the power of the screw air compressor at the current control moment. Moreover, this embodiment dynamically adjusts the differential parameters of the PID controller and regulates the power of the screw air compressor based on the parameters of the dynamically adjusted PID controller, thereby reducing the occurrence of continuous small oscillations such as repeated overshoot and fall of the exhaust pressure of the screw air compressor, thereby improving the control stability of the exhaust pressure of the screw air compressor, that is, improving the control stability of the screw air compressor system.

[0052] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A method for intelligently regulating and controlling the power of a screw air compressor, characterized in that: The method comprises the following steps: Obtaining an actual pressure signal at the current control moment, wherein the actual pressure signal is composed of actual pressure data points, where the abscissa of the actual pressure data point is time and the ordinate is the actual pressure data of the screw air compressor; Performing EMD decomposition on the actual pressure signal to obtain IMM components, and obtaining a current actual pressure data window at the current control moment according to the energy and period values ​​of the IMM components; Obtaining a current deviation window corresponding to the current actual pressure data window based on a difference between the target set pressure value and the actual pressure data in the current actual pressure data window, and obtaining a current deviation fluctuation intensity characterization value at the current control moment based on the deviation in the current deviation window; Obtaining historical deviation fluctuation intensity characterization values ​​at control moments adjacent to the current control moment, obtaining a differential item parameter adjustment factor based on the difference between the historical deviation fluctuation intensity characterization value and the current deviation fluctuation intensity characterization value and the standard deviation of the current deviation window, and using the differential item parameter adjustment factor to adjust the differential item parameter at the control moments adjacent to the current control moment to obtain the differential item parameter at the current control moment; The power of the screw air compressor at the current control moment is controlled by using the differential parameter at the current control moment; The method for obtaining the current actual pressure data window at the current control moment includes: All IMM components are sorted according to energy size to obtain an IMM component sequence, and a sequence to be analyzed is obtained according to the position and energy of the IMM components in the IMM component sequence; the ratio of the energy of each IMM component in the sequence to be analyzed to the cumulative sum of the energies of all IMM components in the sequence to be analyzed is recorded as the weight factor of the corresponding IMM component; the period value of each IMM component in the sequence to be analyzed is calculated, and the product of the weight factor of each IMM component in the sequence to be analyzed and the period value of the corresponding IMM component is used as the weighted period value of the corresponding IMM component; the cumulative sum of the weighted period values ​​of all IMM components in the sequence to be analyzed is calculated and recorded as the target period value at the current control moment; the window constructed by all actual pressure data with an acquisition time in the interval [TL, T] is used as the current actual pressure data window at the current control moment, where T is the current control moment and L is the target period value at the current control moment.

2. The method for intelligently regulating and controlling the power of a screw air compressor according to claim 1, wherein: The method for obtaining the sequence to be analyzed includes: The sum of the energies of all IMM components in the IMM component sequence is recorded as a first total energy. If a ratio of the cumulative sum of the energies of the first N IMM components in the IMM component sequence to the first total energy is greater than a preset proportion threshold, and a ratio of the cumulative sum of the energies of the first N-1 IMM components in the IMM component sequence to the first total energy is not greater than the preset proportion threshold, a new sequence consisting of the first N IMM components in the IMM component sequence is recorded as a sequence to be analyzed.

3. The method for intelligently regulating and controlling the power of a screw air compressor according to claim 1, wherein: The ath deviation in the current deviation window is the result of subtracting the ath actual pressure data in the current actual pressure data window from the target set pressure value.

4. The method for intelligently regulating and controlling the power of a screw air compressor according to claim 1, wherein: The method for obtaining the current deviation fluctuation intensity characterization value includes: The ratio of the absolute value of each deviation in the current deviation window to the cumulative sum of the absolute values ​​of all deviations in the current deviation window is recorded as the weight factor of the corresponding deviation. The product of the square value of each deviation in the current deviation window and the weight factor of the corresponding deviation is calculated and recorded as the weighted deviation of the corresponding deviation. The cumulative sum of the weighted deviations of all deviations in the current deviation window is used as the characterization value of the current deviation fluctuation intensity at the current control moment.

5. The method for intelligently regulating and controlling the power of a screw air compressor according to claim 1, wherein: The method for obtaining the historical deviation fluctuation intensity characterization value is the same as the method for obtaining the current deviation fluctuation intensity characterization value.

6. The method for intelligently regulating and controlling the power of a screw air compressor according to claim 1, wherein: The method for obtaining the differential parameter adjustment factor includes: Obtain the result of subtracting the historical deviation fluctuation intensity characterization value from the current deviation fluctuation intensity characterization value, and record it as the deviation fluctuation change characterization value, determine whether the deviation fluctuation change characterization value is equal to the preset judgment threshold, if so, use the constant 1 as the differential item parameter adjustment factor at the current control moment, otherwise, obtain the differential item parameter adjustment direction characterization value at the current control moment according to the deviation fluctuation change characterization value and the preset judgment threshold, obtain the differential item parameter adjustment amplitude at the current control moment according to the absolute value of the deviation fluctuation change characterization value and the standard deviation of the current deviation window, and multiply the differential item parameter adjustment direction characterization value by the differential item parameter adjustment amplitude and then record the sum of the multiplication of the differential item parameter adjustment direction characterization value and the preset adjustment control coefficient as the differential item parameter adjustment factor at the current control moment.

7. The method for intelligently regulating and controlling the power of a screw air compressor according to claim 6, characterized in that: The method for obtaining the representation value of the differential parameter adjustment direction at the current control moment includes: If the deviation fluctuation change characterization value is greater than the preset judgment threshold, the constant 1 is used as the differential item parameter adjustment direction characterization value at the current control moment; if the deviation fluctuation change characterization value is less than the preset judgment threshold, negative 1 is used as the differential item parameter adjustment direction characterization value at the current control moment.

8. The method for intelligently regulating and controlling the power of a screw air compressor according to claim 6, characterized in that: The method for obtaining the adjustment range of the differential parameter at the current control moment includes: The absolute value of the deviation fluctuation change characterization value is normalized to obtain the normalized deviation fluctuation change characterization value, the standard deviation of the current deviation window is normalized to obtain the normalized deviation standard deviation, the mean of the normalized deviation fluctuation change characterization value and the normalized deviation standard deviation is calculated, and used as the differential parameter adjustment amplitude at the current control moment.

9. The method for intelligently regulating and controlling the power of a screw air compressor according to claim 1, wherein: The differential item parameter at the current control moment is the product of the differential item parameter at the adjacent control moment of the current control moment and the differential item parameter adjustment factor at the current control moment.

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