CN115694287B - Method for restraining oscillation of VF control motor of asynchronous motor - Google Patents
Method for restraining oscillation of VF control motor of asynchronous motor Download PDFInfo
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Abstract
The invention discloses an oscillation suppression method for an asynchronous motor VF control motor, which comprises the following steps of sampling three-phase output current by a frequency converter, obtaining instantaneous reactive current of the asynchronous motor, extracting reactive current oscillation components, outputting an oscillation suppression calculation angle and then outputting an oscillation suppression adjustment angle, simultaneously, sampling bus voltage by the frequency converter, obtaining bus voltage variation, then outputting the oscillation suppression adjustment voltage, finally, calculating the oscillation suppression adjustment angle and a frequency command through a second angle integrator to obtain angle addition, and calculating the oscillation suppression adjustment voltage and the frequency command through a VF curve calculation unit to obtain output voltage addition for SVPWM modulation output. The invention detects the output current and the bus voltage at the same time, increases the angle adjusting output controller and the universal adjusting unit, effectively quickens the control response, realizes the output of the optimal control adjusting quantity, has obvious inhibiting effect and can meet the requirement of parameter consistency of asynchronous motors with different capacities.
Description
Technical Field
The invention belongs to the technical field of VF control methods of asynchronous motors, and particularly relates to a VF control motor oscillation suppression method of an asynchronous motor.
Background
VF control is a common control mode of a frequency converter, has the advantages of simple control mode, no dependence on motor parameters and suitability for most application occasions. VF control belongs to open loop control, and cannot inhibit inherent unstable characteristics of a specific operating frequency during light load or idle running, so that torque fluctuation is generated, continuous oscillation of a motor is caused, meanwhile, the motor current also greatly oscillates, so that a frequency converter is stopped after fault report, the service lives of the motor and other motor equipment can be shortened after long-time continuous oscillation, normal operation cannot be carried out in a specific oscillating frequency section, and the speed regulation range of a VF control mode is limited.
VF control motor oscillations are generally believed to be related to modulation schemes, inverter dead zone effects, reactive exchanges of the frequency converter with the motor, and mechanical frequency resonances of the motor. Because VF control belongs to open loop control, when current oscillation occurs, no effective feedback is used for adjusting the current output, and the oscillation is easy to further deteriorate until the motor or the frequency converter is abnormal.
Aiming at the problem of controlling motor oscillation of the asynchronous motor VF, the motor oscillation is usually inhibited by detecting output current, extracting oscillation factors, adjusting output frequency and stabilizing output torque. The motor oscillation can cause fluctuation of bus voltage at the same time, so that the output voltage is unstable, and further deterioration of the motor oscillation can be effectively avoided by detecting the bus voltage and adjusting and stabilizing the output voltage. In general, motor oscillation presents irregular periodicity, and if the control response is not timely, or the adjustment quantity and the motor oscillation form chase, the motor oscillation cannot be restrained, and even further aggravation of the motor oscillation can be caused.
Therefore, a method for suppressing the oscillation of the VF control motor of the asynchronous motor is needed.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a VF control motor oscillation suppression method for an asynchronous motor.
In order to solve the technical problems, the invention provides the following technical scheme:
the invention provides a method for restraining oscillation of an asynchronous motor VF control motor, which comprises the following steps:
S1, sampling three-phase output current by a frequency converter, and obtaining instantaneous reactive current of an asynchronous motor through a current coordinate converter, wherein the instantaneous reactive current extracts reactive current oscillation components through a first filter and a subtracter;
s2, outputting an oscillation suppression calculation angle by the reactive current oscillation component through a first oscillation suppression calculation unit, and outputting an oscillation suppression adjustment angle by the oscillation suppression calculation angle output controller;
S3, sampling bus voltage by the frequency converter, and calculating to obtain bus voltage variation through a bus voltage sampling value holder and a subtracter, wherein the bus voltage variation outputs oscillation suppression adjustment voltage through a second oscillation suppression calculation unit;
S4, calculating an oscillation suppression adjustment angle and a frequency command through a second angle integrator to obtain angle addition, and calculating an oscillation suppression adjustment voltage and the frequency command through a VF curve calculation unit to obtain output voltage addition for SVPWM modulation output.
The first oscillation suppression calculation unit comprises a first proportional coefficient, a general adjustment unit, an adjustment frequency calculation unit, an adjustment frequency limiting unit and a first angle integrator, wherein the first proportional coefficient is a user adjustable parameter, the reactive current oscillation component is multiplied by the first proportional coefficient and the general adjustment unit to obtain an equivalent voltage adjustment quantity, the adjustment frequency calculation unit is used for obtaining an oscillation suppression adjustment frequency according to the inverse calculation of the slope of a VF curve for the equivalent voltage adjustment quantity, and the oscillation suppression adjustment frequency is subjected to oscillation suppression calculation angle output by the adjustment frequency limiting unit and the first angle integrator.
Preferably, the universal adjusting unit automatically calculates adjusting parameters according to rated output current of the current frequency converter, and is used for adjusting user adjusting parameters of asynchronous motors with different capacities.
Preferably, the adjustment angle output controller accumulates oscillation suppression calculation angles, if the accumulated oscillation suppression calculation angles reach a preset angle threshold, the oscillation suppression adjustment angles are output according to the preset angle threshold, and if the accumulated oscillation suppression calculation angles do not reach the preset angle threshold, the oscillation suppression adjustment angles are not output.
Preferably, the second oscillation suppression calculation unit comprises a second proportionality coefficient and a first adjustment voltage calculation unit, wherein the second proportionality coefficient is a user adjustable parameter, and the first adjustment voltage calculation unit calculates and obtains the oscillation suppression adjustment voltage according to the bus voltage variation.
Preferably, after the converter samples the bus voltage in step S3, the bus voltage further obtains a bus voltage oscillation component through calculation by a second filter and a subtractor, and the bus voltage oscillation component outputs an oscillation suppression adjustment voltage through a third oscillation suppression calculation unit, where the third oscillation suppression calculation unit includes a third scaling factor, a second adjustment voltage calculation unit, and an adjustment voltage limiting unit, the third scaling factor is a user adjustable parameter, the second adjustment voltage calculation unit calculates according to the bus voltage oscillation component to obtain an oscillation suppression adjustment voltage, and the adjustment voltage limiting unit limits a maximum value and a minimum value of the oscillation suppression adjustment voltage.
Preferably, the first filter reduces the filtering effect in the low-frequency stage to avoid starting abnormality, and the adjusting frequency amplitude limiting unit reduces the frequency amplitude limiting value in the low-frequency stage to avoid abnormality caused by overlarge output oscillation suppression adjusting frequency.
Compared with the prior art, the invention has the following beneficial effects:
Firstly, the invention detects the output current and the bus voltage at the same time, and links such as an angle adjustment output controller, a general adjusting unit and the like are added, so that the control response can be effectively quickened, the output of the optimal control adjustment quantity is realized, the inhibition effect is obvious, the requirement of parameter consistency of asynchronous motors with different capacities can be met, and the invention has good practical value.
According to the invention, by adding the universal adjusting unit, corresponding adjusting parameters are automatically calculated according to the current rated output current, rated output voltage and other easily-obtained parameters of the frequency converter, and the oscillation suppression of asynchronous motors with different capacities can be realized without adjusting or only trimming user parameters, so that the parameter consistency is good.
Thirdly, the invention avoids the problem that the motor oscillation cannot be effectively restrained by adding the link of the oscillation restraining calculation angle accumulated output and the chasing formed by the oscillation restraining adjustment quantity and the motor oscillation, and simultaneously, the single adjustment quantity is too small under the condition of high carrier wave, so that the restraining effect is poor.
Fourth, since the motor oscillation causes unstable energy exchange between the frequency converter and the motor, and causes fluctuation of bus voltage, the invention also regulates the output voltage by detecting the change of bus voltage, and prevents further deterioration of motor oscillation caused by fluctuation of the output voltage by stabilizing the output voltage.
Drawings
Fig. 1 is a flowchart of a method for suppressing oscillation of an asynchronous motor VF control motor according to an embodiment of the present invention;
fig. 2 is a block diagram of a first oscillation suppression calculating unit according to an embodiment of the present invention;
FIG. 3 is a block diagram of a second oscillation suppression calculating unit according to the first embodiment of the present invention;
fig. 4 is a flowchart of an operation flow of a method for suppressing oscillation of an asynchronous motor VF control motor according to the second embodiment of the present invention;
Fig. 5 is a block diagram of a third oscillation suppression calculating unit in the second embodiment of the present invention;
FIG. 6 is a graph comparing currents of a frequency converter driving 7.5Kw asynchronous motor at 25Hz without and with the suppression method of the present invention.
Detailed Description
The preferred embodiments of the present invention will be described below with reference to the accompanying drawings, it being understood that the preferred embodiments described herein are for illustration and explanation of the present invention only, and are not intended to limit the present invention.
The first embodiment is as follows:
the embodiment provides a method for suppressing oscillation of an asynchronous motor VF control motor, which comprises the following steps:
S1, sampling three-phase output current by a frequency converter, acquiring instantaneous reactive current of an asynchronous motor through a current coordinate converter, and extracting reactive current oscillation components of the instantaneous reactive current through a first filter and a subtracter;
As shown in fig. 1, an output current sampling unit samples three-phase output current, an instantaneous reactive current i_d and an instantaneous active current i_q are obtained through calculation of a current coordinate converter, the instantaneous reactive current i_d can obtain a reactive current direct current component i_d_lpf through a first filter, and a reactive current oscillation component delta i_d=i_d_lpf-i_d is obtained through calculation of a subtracter.
S2, outputting an oscillation suppression calculation angle through a first oscillation suppression calculation unit by the reactive current oscillation component, and outputting an oscillation suppression adjustment angle through an adjustment angle output controller by the oscillation suppression calculation angle;
as shown in fig. 2, the first oscillation suppression calculating unit includes a first scale factor, a general adjusting unit, an adjusting frequency calculating unit, an adjusting frequency clipping unit, and a first angle integrator;
the first scale factor is a user adjustable parameter, noted as K_p1;
The universal regulating unit automatically calculates regulating parameters according to the rated output current of the current frequency converter and records the regulating parameters as K_a, wherein K_a=V_m/I_m is K_m, V_m is the input voltage of the frequency converter, I_m is the rated output current of the frequency converter, and K_m is the identification coefficient of the built-in type of the frequency converter;
The reactive current oscillation component is multiplied by a first proportional coefficient and a general regulating unit to obtain an equivalent voltage regulating quantity, and the equivalent voltage regulating quantity is recorded as V delta id;
The adjusting frequency calculating unit obtains oscillation suppression adjusting frequency f_adj according to the slope back calculation of the VF curve for the equivalent voltage adjusting quantity V_delta id, namely f_adj=V_delta id×f_base/V_base, wherein f_base is the base frequency of the VF curve, and V_base is the base voltage of the VF curve;
the oscillation suppression adjusting frequency f_adj outputs an oscillation suppression calculation angle through the adjusting frequency limiting unit and the first angle integrator;
the adjusting frequency amplitude limiting unit sets the maximum amplitude limiting value f_adj_max of the oscillation suppression adjusting frequency, and in general, when in low-frequency operation, f_adj_max is required to be correspondingly reduced, so that abnormal operation caused by larger oscillation suppression adjusting frequency is avoided;
The first angle integrator is used for performing angle integration on the oscillation suppression adjusting frequency f_adj to obtain an oscillation suppression calculating angle theta_cal;
The adjustment angle output controller accumulates the oscillation suppression calculation angles θ_cal, outputs the oscillation suppression adjustment angles θ_adj=θ_thr if the accumulated oscillation suppression calculation angles reach a preset angle threshold θ_thr, and outputs the oscillation suppression adjustment angles θ_adj=0 if the accumulated oscillation suppression calculation angles do not reach the preset angle threshold θ_thr.
S3, sampling bus voltage by the frequency converter, calculating bus voltage variation through a bus voltage sampling value holder and the subtracter, and outputting oscillation suppression adjustment voltage through a second oscillation suppression calculation unit by the bus voltage variation;
As shown in fig. 1, a busbar voltage sampling unit samples a direct current busbar voltage v_pn, reads a previous period of sampled busbar voltage v_pn_last through a busbar voltage sampling value holder, calculates a busbar voltage variation Δv_pn1=v_pn_last-v_pn through a subtracter, and obtains an oscillation suppression adjustment voltage v_d_adj1 through a second oscillation suppression calculation unit;
as shown in fig. 3, the second oscillation suppression calculating unit includes a second scaling factor, an adjustment voltage calculating unit;
the second proportionality coefficient is a user adjustable parameter and is marked as K_p2;
The first regulating voltage calculating unit determines the relation between the bus voltage and the output voltage of the inverter according to the mathematical model of the inverter, and takes common SVPWM modulation as an example, the regulating voltage is regulated by oscillation suppression ;
By the second oscillation suppression calculating unit, the problem that the calculated value of the modulation output voltage deviates from the actual value due to the oscillation condition of the bus voltage is corrected, so that the output voltage can be kept stable under the condition that the bus voltage wave is caused by the motor oscillation, and further deterioration of the motor oscillation due to the fluctuation of the output voltage is avoided.
S4, calculating the oscillation suppression adjustment angle and the frequency command through an angle integrator to obtain angle addition, and calculating the oscillation suppression adjustment voltage and the frequency command through a VF curve calculation unit to obtain output voltage addition for SVPWM modulation output;
As shown in fig. 1, a current frequency command f_ref is calculated by a speed curve, an output voltage V_ref is calculated by the frequency command f_ref according to a VF curve, a voltage vector angle theta_ref is obtained by the frequency command f_ref through an angle integrator 2, a final output voltage is obtained by adding the output voltage V_ref and an oscillation suppression adjustment voltage V_d_adj1, a final output voltage vector angle is obtained by adding the voltage vector angle theta_ref and the oscillation suppression adjustment angle theta_adj, and the final output voltage vector angle are used for calculation and output by a SVPWM modulation unit;
As shown in fig. 6, according to the control method of the present embodiment, which is not adopted (the left half in fig. 6) and adopted (the right half in fig. 6), the current comparison chart of the inverter driving 7.5Kw asynchronous motor at 25Hz is compared, and it can be seen from the comparison that the control method provided by the present invention can quickly and effectively suppress motor oscillation.
The second embodiment is as follows:
As another preferred embodiment, the rest is the same as embodiment one except that in this embodiment, after the converter samples the bus voltage, the bus voltage is also calculated by the second filter and the subtractor to obtain a bus voltage oscillation component, and the bus voltage oscillation component outputs the oscillation suppression adjustment voltage by the third oscillation suppression calculation unit.
As shown in fig. 4, the busbar voltage sampling unit samples a dc busbar voltage v_pn, the busbar voltage v_pn_lpf is obtained by a second filter, the busbar voltage fluctuation amount Δv_pn2=v_pn_lpf-v_pn is obtained by a subtractor calculation, and the busbar voltage fluctuation amount Δv_pn2 is passed through a third oscillation suppression calculation unit to obtain an oscillation suppression adjustment voltage v_d_adj2;
as shown in fig. 5, the third oscillation suppression calculating unit includes a third scaling factor, a second adjustment voltage calculating unit, and an adjustment voltage clipping unit;
the third scaling factor is a user-adjustable parameter, noted K_p3;
the second adjusting voltage calculating unit determines the relation between the bus voltage and the inverter output voltage according to the mathematical model of the inverter, and takes common SVPWM modulation as an example, the oscillation suppression adjusting voltage ;
The regulating voltage limiting unit is used for limiting the output range of the oscillation suppression regulating voltage V_d_adj2, wherein the minimum value of the V_d_adj2 is set to avoid normal bus voltage fluctuation, and the oscillation suppression based on output reactive current can be realized preferentially, and the maximum value of the V_d_adj2 is set to avoid motor abnormality caused by abnormal output voltage regulation.
It should be noted that the above-mentioned embodiments are merely preferred embodiments of the present invention, and the present invention is not limited thereto, but may be modified or substituted for some of the technical features thereof by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103973189A (en) * | 2014-04-04 | 2014-08-06 | 合康变频科技（武汉）有限公司 | Method and device for oscillation suppression of variable frequency drive asynchronous motor |
| CN104467597A (en) * | 2013-09-16 | 2015-03-25 | 伊顿公司 | V/F control method for inhibiting induction motor current oscillation |
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| CN112260225B (en) * | 2020-09-08 | 2023-08-18 | 中国电力科学研究院有限公司 | Method and system for calculating three-phase short-circuit current of doubly-fed wind turbine generator based on combined model |
| CN112737445B (en) * | 2020-12-25 | 2022-11-22 | 中车永济电机有限公司 | Control method for oscillation suppression of permanent magnet auxiliary synchronous reluctance motor |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104467597A (en) * | 2013-09-16 | 2015-03-25 | 伊顿公司 | V/F control method for inhibiting induction motor current oscillation |
| CN103973189A (en) * | 2014-04-04 | 2014-08-06 | 合康变频科技（武汉）有限公司 | Method and device for oscillation suppression of variable frequency drive asynchronous motor |
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