CN113985808B - Load switching path optimizing method based on minimum step disturbance - Google Patents
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- G—PHYSICS
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- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
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- G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
- G05B19/19—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
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- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
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Abstract
A load switching path optimizing method based on minimum step disturbance belongs to the technical field of compressor load adjustment. The technical scheme is characterized by comprising the following steps: step one, calculating a curve equation of combined adjustment of turning speed and cylinder unloading; calculating the coordinates of the working state points of the target load according to a distance nearest method; step three, comparing the smaller values of the current load and the target load, and calculating a first load step adjusting point coordinate at the smaller value of the load according to a load overshoot threshold method; and step four, calculating coordinates of a second load step regulating point of a curve where the first load step regulating point is in step to a larger load value under the condition that the rotating speed value of the transverse axis is unchanged, and finally obtaining a minimum step disturbance load switching path under the condition of the load overshoot of the allowable air quantity. The invention realizes the load switching with minimum step disturbance, effectively reduces the step fluctuation in the load switching, and improves the regulation performance.
Description
Technical Field
The invention belongs to the technical field of compressor load regulation, and relates to a load switching path optimizing method based on minimum step disturbance.
Background
When the process is changed or the air source fluctuates, in order to keep the process stable and realize the economic operation of the compressor, the air load of the compressor needs to be adjusted to adapt to the continuously changing air demand, and the load adjustment process is actually the switching from the current load to the preset load. Common adjusting modes include driver rotation speed adjustment, partial stroke pressure opening air inlet valve adjustment, cylinder unloading step adjustment and the like.
The partial stroke pressure opening air inlet valve is regulated by adding a loading and unloading device on the air inlet valve to delay the closing time of the air suction valve, so that the air actively flows back to reduce the exhaust gas quantity, and the return air is in a low-pressure state and is not compressed, thereby effectively reducing the power consumption in the regulating mode. However, in the method, each air valve is required to be provided with a precise servo control device to drive the unloading device to act, the frequency of the action is required to be equal to that of the air valve of the compressor, and the response speed and the service life of the whole driving device are very high. These disadvantages limit the application range of the method, and at present, most of the methods are applied to low-speed compressors, and cannot realize effective adjustment on middle-high-speed compressors.
Drive motor speed adjustment and cylinder unloading step adjustment are two conventional adjustment methods. The reduction of the rotating speed easily causes the adverse effects of insufficient lubrication, increased vibration, reduced output torque and the like of the unit, and the rotating speed adjustment range is limited. If the exhaust gas quantity is to be reduced, other auxiliary regulating measures are required. The cylinder unloading step adjustment can only provide step adjustments, such as 100%, 75%, 50%, 25%, 0 five speed adjustments for a two cylinder double acting compressor. The combination regulation of the rotation speed regulation of the driving machine and the unloading step regulation of the cylinder overcomes the defects of the two technologies, and the continuous stepless regulation of the load in the range of 0-100% can be realized. However, in the combined regulation mode, the switching from the current load to another load needs to be realized, and the unloading step regulation gear and the rotation speed value of the cylinder are required to be regulated simultaneously, so that larger process fluctuation is easy to cause, and therefore, the realization of the load switching with minimum step disturbance is an effective measure for improving the regulation performance and improving the switching regulation capacity of each load section.
Disclosure of Invention
The invention aims to overcome the defects of the existing load regulation technology, provides a load switching path optimizing method based on minimum step disturbance, solves the problem of large process fluctuation of a load switching unit, improves the regulation performance and improves the switching regulation capacity of each load section.
The technical aim of the invention is realized by the following technical scheme:
1) If the number of the first-stage cylinders is k and the cylinders are double-acting, 2k+1-stage stepped regulation of the air quantity can be realized through stepped regulation of cylinder unloading, and the regulation step length percentage of each stage is as follows
2) Setting the working gas volume load ratio of the reciprocating compressor as eta (eta E [0,1 ]), and obtaining the straight line group regulated by combining rotation speed regulation and cylinder unloading asWhere i (i=0, 1, …,2 k) is a parameter, n max is the rated rotational speed of the compressor, n (n e [ n min,nmax ]) is the actual rotational speed (r/min) of the compressor, and n min is the minimum value of the rotational speed adjustment. Let n=n min, get the straight line family load minimum value boundary point of the combination adjustment of turning speed and cylinder unloading as/>Where i=0, 1, …,2k.
3) Let the coordinates of the current working state point I of the compressor beN I is the current rotation speed of the compressor, eta I is the current gas load of the compressor, and the linear parameter i=ζ I where the current working state point is located is further obtained by the point coordinates; the target load of compressor regulation is known as eta II, the set of solving the linear family equation carried into 2) is [ ζ II-j,nII-j ], wherein ζ II-j is the linear parameter, n II-j is the target regulation rotating speed, and j is the positive integer parameter.
4) Calculating a target load solution closest to the linear parameter where the current working state point is located: min { |ζ I-ξII-j }, where j=1, 2,3, …; assuming that the obtained target solution is [ ζ II,nII ], obtaining the coordinate of the target working state point II as follows
5) The linear equation of the current working state point I is obtained by the linear parameter i=ζ I And then obtaining a linear equation/>, by the linear parameter i=ζ II of the target working state point IIDetermining allowable gas load overshoot epsilon, generally taking epsilon (0,0.15), wherein the higher the accuracy requirement of process adjustment is, the smaller the value of epsilon is, and comparing the sizes of eta I and eta II:
(1) If eta I＝ηII, the load is equal and the switching is not needed;
(2) If eta I＞ηII, calculating on the straight line where the target working state point II is located to obtain the coordinate of the load step adjustment point A as follows Further calculating on the straight line where the current working state point I is positioned to obtain the coordinate of the load step-change adjusting point B as/>Finally, the minimum step disturbance load switching path under the condition of the allowable gas load overshoot is obtained as a current working state point I, a straight line where the current working state point I is located, a load step adjustment point B, a load step adjustment point A and a target working state point II;
(3) If eta I＜ηII, calculating on the straight line where the current working state point I is located to obtain the coordinate of the load step adjustment point A as follows Further calculating on the straight line where the target working state point II is located to obtain the coordinate of the load step-change adjusting point B as/>Finally, the minimum step disturbance load switching path under the condition of the allowable gas load overshoot is obtained as a current working state point I, a straight line where the current working state point I is located, a load step adjustment point A, a load step adjustment point B and a target working state point II;
The load switching path optimizing method realizes the load switching with minimum step disturbance, effectively reduces the step fluctuation in the load switching, and improves the regulation performance.
Description of the drawings:
FIG. 1 is a combined compressor speed and cylinder unloading adjustment graph with k double acting cylinders;
FIG. 2 is a 2-cylinder compressor speed and cylinder unloading combination modulation plot;
FIG. 3 is a load switching path in a 2-cylinder compressor speed and cylinder unloading combination modulation mode;
FIG. 4 is a minimum step disturbance load switching path for a 2-cylinder compressor when η I＞ηII;
FIG. 5 is a minimum step disturbance load switching path for a 2-cylinder compressor when η I＞ηII;
Detailed Description
The principles and embodiments of the present invention are described in detail below with reference to the drawings.
A) Referring to fig. 1, for a compressor with k double-acting cylinders at one stage, 2k+1 stage step adjustment of gas load can be achieved by cylinder unloading step adjustment, with the percentage of adjustment steps at each stage beingUnder the step load of the i th gear of the cylinder unloading, the combined regulation curve/> is obtained by combining the rotation speed regulationWherein ii (i=0, 1, …,2 k) is a parameter, n max is the rated speed of the compressor, and the abscissa is the speed percentage/>The ordinate is the load percentage η. Under the step load of the ith gear, the load is reduced from the maximum value/>, along with the reduction of the rotating speedGradually decreasing to a load minimum boundary point M i: /(I)Where n min is the minimum value of the rotational speed adjustment.
B) Referring to fig. 2, taking a one-stage two-cylinder double-acting reciprocating compressor as an example, 4 adjusting lines are obtained under the combined adjustment of turning speed and cylinder unloading, 0, 25%, 50%, 75% and 100% of step adjustment is finished through cylinder unloading step adjustment, and stepless continuous adjustment of load from maximum to minimum value boundary points is realized through reducing the rotating speed under each step. In this example, the rotational speed value corresponding to the point n max＝1000RPM,M1～M4 of the compressor is 600RPM. For example, in a 100% adjustment gear, all cylinders are fully loaded, and the load is adjusted from 100% to the point M 4 (60% and 60%) by adjusting the rotation speed; in 75% adjusting gear, one side of one cylinder is unloaded, the other cylinders are full, and the load is adjusted from 75% to the point M 3 (60% and 45%) by adjusting the rotating speed. The presence of an overlap region on the two adjustment lines, see the square region in fig. 2, means that adjustment of the same load can be achieved by different cylinder unloading and speed combinations.
C) Referring to fig. 3, taking the example that the current working state point i is located at the coordinates (80% ), and the target working state point ii is located at the coordinates (70%, 35%), the load switching path includes:
Path one: firstly, keeping the rotation speed unchanged at a current working state point I, namely, reducing the rotation speed to a point (80 percent, 40 percent) of a straight line ③ through cylinder unloading, and reducing the rotation speed to a target working state point II along a straight line ③ through adjustment, wherein the step of the load under the path is maximum, the step value is 40 percent, the minimum point of the medium load is point II, and the overshoot is 0; the path is a switching path commonly used at present, the adjusting method is simple, but the step fluctuation in the switching process is the largest, and the impact on a process pipeline is large.
Path two: firstly, reducing the rotating speed to a point M 4 (60 percent ) along a straight line ① where a current working state point I is located by adjusting the rotating speed, maintaining the rotating speed unchanged at a point M 4, unloading the rotating speed to a point M 2 (60 percent, 30 percent) through a cylinder, and then increasing the rotating speed to a target working state point II (70 percent, 35 percent) along a straight line ③ from a point M 2 by adjusting the rotating speed, wherein the step of the load under the path is minimum, the step value is 30 percent, the lowest load point in the adjustment is the point M 2, but a load section lower than a target value exists in the adjustment process, and a certain overshoot is generated;
And path III: the rotational speed is reduced to any point between the point M 4 and the state point i along the straight line ① where the current operating state point i is located by adjusting the rotational speed, the rotational speed is kept unchanged by the point, and is stepped to the straight line ③ through cylinder unloading, and then the rotational speed is adjusted to the target operating state point ii along the straight line ③ by adjusting the rotational speed. The step in load under the path is between path one and path two.
D) Referring to fig. 4, when η I＞ηII is calculated on the straight line where the target operating state point ii is located, the coordinates of the load step adjustment point a are calculated asGiven the point i coordinates (80% ), the point ii coordinates (70%, 35%), epsilon=3% for the example of fig. 4, the point a coordinates (64%, 32%); further calculating on the straight line where the current working state point I is positioned to obtain the coordinate of the load step-change adjusting point B as/>I.e. B coordinates (64% ); and finally obtaining the minimum step disturbance load switching path under the condition that the allowable gas quantity load overshoot epsilon=3% as the current working state point I, the load step adjustment point B, the load step adjustment point A and the target working state point II. Compared with the conventional direct step-type switching path, the step disturbance of the path is reduced by 8%, and the overshoot meets the process regulation requirement.
E) Referring to FIG. 5, when η I＜ηII, the coordinates of the load step adjustment point A are calculated on the straight line where the current operating state point I is located asKnowing the point i coordinates (84%, 21%), the point ii coordinates (66%, 33%), epsilon=3% and the point a coordinates (72%, 18%) in the example of fig. 5; further calculating on the straight line where the target working state point II is located to obtain the coordinate of the load step-change adjusting point B as/>I.e. B has a coordinate of (72%, 36%); and finally obtaining the minimum step disturbance load switching path under the condition that the allowable gas quantity load overshoot epsilon=3% as the current working state point I, the load step adjustment point A, the load step adjustment point B and the target working state point II. And compared with the conventional direct step-type switching path, the step disturbance of the path is reduced by 3%, and the overshoot meets the process regulation requirement.
Compared with the common direct step type switching, the load switching path optimizing method effectively reduces step fluctuation in load switching, and the switching method has better optimizing effect when the difference between the current load and the target load is larger.
Claims (1)
1. The load switching path optimizing method based on the minimum step disturbance is characterized by comprising the following steps of:
1) Let the number of first-stage cylinders be k, the cylinders are double-acting, 2k+1-stage ladder regulation of the air quantity is realized through the ladder regulation of cylinder unloading, and the regulation step length percentage of each stage is as follows
2) Setting the working gas volume load ratio of the reciprocating compressor as eta (eta E [0,1 ]), and obtaining the straight line group regulated by combining rotation speed regulation and cylinder unloading asWherein i is a parameter, n max is the rated rotation speed of the compressor, n is the actual rotation speed (r/min) of the compressor, and n epsilon [ n min,nmax];nmin ] is the minimum value of rotation speed adjustment; let n=n min, get the straight line family load minimum value boundary point of the combination adjustment of turning speed and cylinder unloading as/>Wherein i=0, 1,..2 k;
3) Let the coordinates of the current working state point I of the compressor be N I is the current rotation speed of the compressor, eta I is the current gas load of the compressor, and the linear parameter i=ζ I where the current working state point is located is further obtained by the point coordinates; knowing that the target load regulated by the compressor is eta II, bringing the target load into a straight line family equation in 2), and obtaining a solution set of [ ζ II-j,nII-j ], wherein ζ II-j is a straight line parameter, n II-j is a target regulating rotating speed, and j is a positive integer parameter;
4) Calculating a target load solution closest to the linear parameter where the current working state point is located: min { |ζ I-ξII-j | } where j=1, 2,3,; assuming that the obtained target solution is [ ζ II,nII ], obtaining the coordinate of the target working state point II as follows
5) The linear equation of the current working state point I is obtained by the linear parameter i=ζ I And then obtaining a linear equation/>, by the linear parameter i=ζ II of the target working state point IIDetermining allowable gas load overshoot epsilon, taking epsilon (0,0.15), wherein the higher the accuracy requirement of process adjustment is, the smaller the value of epsilon is, and comparing the sizes of eta I and eta II:
(1) If eta I＝ηII, the load is equal and the switching is not needed;
(2) If eta I＞ηII, calculating on the straight line where the target working state point II is located to obtain the coordinate of the load step adjustment point A as follows Further calculating on the straight line where the current working state point I is positioned to obtain the coordinate of the load step-change adjusting point B as/>Finally, the minimum step disturbance load switching path under the condition of the allowable gas quantity load overshoot is obtained as a current working state point I, a straight line where the current working state point I is located, a load step adjustment point B, a load step adjustment point A and a target working state point II;
(3) If eta I＜ηII, calculating on the straight line where the current working state point I is located to obtain the coordinate of the load step adjustment point A as follows Further calculating on the straight line where the target working state point II is located to obtain the coordinate of the load step-change adjusting point B as/>And finally obtaining the minimum step disturbance load switching path under the condition of the allowable gas quantity load overshoot as a current working state point I, a straight line where the current working state point I is located, a load step adjustment point A, a load step adjustment point B and a target working state point II.
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