CN117254740A - Asynchronous motor current determination method and device - Google Patents
Asynchronous motor current determination method and device Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
- H02P23/14—Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P2207/00—Indexing scheme relating to controlling arrangements characterised by the type of motor
- H02P2207/01—Asynchronous machines
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Abstract
The invention discloses a method and a device for determining current of an asynchronous motor, and relates to the technical field of asynchronous motors. According to the invention, the target exciting current corresponding to the required torque is determined according to the first corresponding relation between the motor torque and the exciting current, and the target torque current corresponding to the target exciting current is determined according to the second corresponding relation between the exciting current and the torque current, so that the optimal control current of the asynchronous motor corresponding to the required torque can be rapidly determined.
Description
Technical Field
The invention relates to the technical field of asynchronous motors, in particular to a method and a device for determining current of an asynchronous motor.
Background
Asynchronous motors have the advantage of low cost, less drag torque, and less overall efficiency relative to permanent magnet synchronous motors. In order to increase the operating efficiency of an asynchronous motor, it is necessary to use optimal current control at each required torque. Therefore, how to determine the optimal control current of an asynchronous motor is a problem to be solved.
Disclosure of Invention
The invention solves the technical problem of how to determine the optimal control current of the asynchronous motor by providing the method and the device for determining the current of the asynchronous motor.
In one aspect, the present invention provides the following technical solutions:
an asynchronous motor current determination method, comprising:
acquiring a required torque of an asynchronous motor;
determining a target exciting current corresponding to the required torque according to a first corresponding relation between the motor torque and the exciting current;
and determining a target torque current corresponding to the target exciting current according to a second corresponding relation between the exciting current and the torque current.
Optionally, the first corresponding relation is a table for recording excitation current points corresponding to each motor torque point under a fixed torque step length;
the determining the target exciting current corresponding to the required torque according to the first corresponding relation between the motor torque and the exciting current comprises the following steps:
acquiring exciting current points corresponding to two motor torque points adjacent to the required torque in the first corresponding relation; and carrying out linear weighting on the two exciting current points to obtain the target exciting current.
Optionally, the second correspondence is a table for recording torque current points corresponding to each exciting current point;
the determining the target torque current corresponding to the target exciting current according to the second corresponding relation between the exciting current and the torque current comprises:
acquiring the torque current points corresponding to two exciting current points adjacent to the target exciting current in the second corresponding relation;
and linearly weighting the two torque current points to obtain the target torque current.
Optionally, before the step of obtaining the required torque of the asynchronous motor, the method further includes:
establishing a first expression of stator inductance and the exciting current;
establishing a second expression of the motor torque, the exciting current and the torque current according to the first expression;
obtaining an extremum function expression of the second expression;
dominating the extremum function expression to obtain a third expression of the torque current and the exciting current;
obtaining a motor torque-exciting current curve according to the second expression and the third expression; establishing the first corresponding relation according to the motor torque-exciting current curve;
and establishing the second corresponding relation according to the third expression.
Optionally, the second expression is:t is the torque of the motor, N p Is the pole pair number of the motor, alpha is the proportional coefficient of the leakage inductance of the stator and the inductance of the stator, and f (i) sd ) For the first expression, isd is the excitation current, and isq is the torque current.
Optionally, the third expression is:or (b)
a0, a1, a2, a3, b1, b2, b3, w are fourier expression coefficients;
p1, p2, p3 are polynomial expression coefficients.
Optionally, before the establishing the first expression of the stator inductance and the excitation current, the method further includes:
acquiring a plurality of different stator Q-axis voltages corresponding to the exciting currents;
calculating the stator inductance corresponding to each exciting current according to the Q-axis voltage of each stator and the corresponding exciting current;
and establishing the first expression according to a plurality of stator inductances and the corresponding exciting currents.
On the other hand, the invention also provides the following technical scheme:
an asynchronous motor current determining device, comprising:
the acquisition module is used for acquiring the required torque of the asynchronous motor;
the determining module is used for determining a target exciting current corresponding to the required torque according to a first corresponding relation between the motor torque and the exciting current;
and determining a target torque current corresponding to the target exciting current according to a second corresponding relation between the exciting current and the torque current.
Optionally, the first corresponding relation is a table for recording excitation current points corresponding to each motor torque point under a fixed torque step length;
the determining module is further configured to: acquiring exciting current points corresponding to two motor torque points adjacent to the required torque in the first corresponding relation; and carrying out linear weighting on the two exciting current points to obtain the target exciting current.
Optionally, the second correspondence is a table for recording torque current points corresponding to each exciting current point;
the determining module is further configured to: acquiring the torque current points corresponding to two exciting current points adjacent to the target exciting current in the second corresponding relation; and linearly weighting the two torque current points to obtain the target torque current.
Optionally, the asynchronous motor current determining device further includes: the building module is used for building a first expression of the stator inductance and the exciting current; establishing a second expression of the motor torque, the exciting current and the torque current according to the first expression; obtaining an extremum function expression of the second expression; dominating the extremum function expression to obtain a third expression of the torque current and the exciting current; obtaining a motor torque-exciting current curve according to the second expression and the third expression; determining the first corresponding relation according to the motor torque-exciting current curve; and determining the second corresponding relation according to the third expression.
Optionally, the second expression is:t is the torque of the motor, N p Is the pole pair number of the motor, alpha is the proportional coefficient of the leakage inductance of the stator and the inductance of the stator, and f (i) sd ) For the first expression, isd is the excitation current, isq is the torque current optional, and the third expression is: />Or (b)
a0, a1, a2, a3, b1, b2, b3, w are fourier expression coefficients;
p1, p2, p3 are polynomial expression coefficients.
Optionally, the establishing module is further configured to: acquiring a plurality of different stator Q-axis voltages corresponding to the exciting currents; calculating the stator inductance corresponding to each exciting current according to the Q-axis voltage of each stator and the corresponding exciting current; and establishing the first expression according to a plurality of stator inductances and the corresponding exciting currents.
On the other hand, the invention also provides the following technical scheme:
an electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing any of the asynchronous motor current determination methods described above when executing the computer program.
On the other hand, the invention also provides the following technical scheme:
a computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements any of the asynchronous motor current determination methods described above.
The one or more technical schemes provided by the invention have at least the following technical effects or advantages:
according to the invention, the target exciting current corresponding to the required torque is determined according to the first corresponding relation between the motor torque and the exciting current, and the target torque current corresponding to the target exciting current is determined according to the second corresponding relation between the exciting current and the torque current, so that the optimal control current of the asynchronous motor corresponding to the required torque can be rapidly determined.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for determining current of an asynchronous motor in an embodiment of the invention;
FIG. 2 is a schematic diagram of a motor torque versus field current curve in an embodiment of the present invention;
FIG. 3 is a schematic diagram of an excitation current versus torque current curve in an embodiment of the present invention;
fig. 4 is a schematic diagram of an asynchronous motor current determining device in an embodiment of the invention.
Detailed Description
The embodiment of the invention solves the technical problem of how to determine the optimal control current of the asynchronous motor by providing the method and the device for determining the current of the asynchronous motor.
In order to better understand the technical scheme of the present invention, the following detailed description will refer to the accompanying drawings and specific embodiments.
As shown in fig. 1, the method for determining current of an asynchronous motor according to an embodiment of the present invention includes:
step S1, obtaining the required torque of an asynchronous motor;
step S2, determining a target exciting current corresponding to the required torque according to a first corresponding relation between the motor torque and the exciting current;
and step S3, determining a target torque current corresponding to the target exciting current according to a second corresponding relation between the exciting current and the torque current.
Before step S1, the embodiment of the present invention further needs to establish a first corresponding relationship and a second corresponding relationship in advance, so before step S1, the method for determining current of an asynchronous motor further includes:
acquiring stator Q-axis voltages corresponding to a plurality of different exciting currents; calculating a stator inductance corresponding to each exciting current according to the Q-axis voltage of each stator and the corresponding exciting current; establishing a first expression of the stator inductance and the exciting current according to the plurality of stator inductances and the corresponding exciting currents; establishing a second expression of motor torque, exciting current and torque current according to the first expression; obtaining an extremum function expression of the second expression; the extremum function expression is made dominant, and a third expression of the torque current and the exciting current is obtained; obtaining a motor torque-exciting current curve according to the second expression and the third expression; establishing a first corresponding relation according to a motor torque-exciting current curve; and establishing a second corresponding relation according to the third expression.
The speed difference of the asynchronous motor is given as 0, the torque current is given as 0, the exciting current isd is given by a fixed step length isd_step, and the stator Q axis voltage Usq corresponding to each exciting current isd is recorded.
U Sq ＝ω·L s ·i sd ω is the stator current frequency and Ls is the stator inductance. Calculating to obtain stator inductances Ls corresponding to different exciting currents isd according to the previous formula; fitting a plurality of data points (isd, ls) on Matlab yields the curve equation ls=f (isd) of Ls and isd, i.e. the first expression.
The present invention provides two first expressions:
first, the first expression is a Fourier expression,a0, a1, a2, a3, b1, b2, b3, w are fourier expression coefficients;
the second, the first expression is a polynomial expression,p1, p2, p3 are polynomial expression coefficients.
The asynchronous motor torque is related to motor inductance parameters, exciting current and torque current, wherein the inductance parameters are related to the exciting current, so that the motor torque and the exciting current are not in simple primary relation, and the relation between the inductance parameters and the exciting current is required to be reacted into the motor torque.
Approximately equalizing the stator leakage inductance and the rotor leakage inductance, and enabling:
L σs ＝α·L s ，L σs the stator leakage inductance is alpha, and the proportion coefficient of the stator leakage inductance and the stator inductance is alpha;
the torque expression may be converted to:
i.e. the second expression, T is the motor torque, N p For the motor pole pair number, isq is the torque current.
And (3) solving an extremum function expression of motor torque relative to isd and isq binary functions under the additional condition of a fixed current vector by utilizing a Lagrange extremum method, wherein the additional condition is as follows:
i s vector current for the motor;
the Lagrangian auxiliary function is:
gamma is the Lagrangian multiplier;
the auxiliary function H deflects isd and isq and makes them equal to 0, so as to obtain:
and the two equations are combined to obtain an extremum function expression:
is the derivative of Ls with respect to isd;
if the first expression is a Fourier expression, then
And dominating the extremum function expression by Matlab:
syms isd isq a0 a1 a2 a3 b1 b2 b3 w
a third expression is obtained:
in the embodiment of the present invention, a0= 0.001733, a1= -0.0003476, b1= -0.002001, a2= -0.0008352, b2= 0.0004825, a3= 0.0001485, b3=0.0001686, and w= 0.006981 may be selected, and α is taken as an empirical value of 0.95.
If the first expression is a polynomial expression, a third expression may be obtained:
in the embodiment of the present invention, p1= -5.098, p2=4784, p3=4.798e+04 may be selected. The first expression is a polynomial expression, the derivative process would be very simple, but the fitting accuracy is slightly worse than the fourier one.
After the second expression and the third expression are obtained, a motor torque-exciting current curve can be further obtained according to the second expression and the third expression, as shown in fig. 2.
According to the embodiment of the invention, the expression of the motor torque-exciting current curve can be directly used as a first corresponding relation, and the third expression is used as a second corresponding relation, so that after the required torque of the asynchronous motor is obtained, the required torque can be input into the expression of the motor torque-exciting current curve to obtain the target exciting current, and the target exciting current is input into the third expression to obtain the target torque current, but the realization is difficult in practice.
Here, a motor torque-exciting current curve and a torque current-exciting current curve corresponding to the third expression may be respectively drawn in MATLAB, as shown in fig. 3, a fixed torque step (e.g. 10 n.m) is set, exciting current points under each motor torque point are found and recorded on the motor torque-exciting current curve, and torque current points under each exciting current point are found and recorded on the torque current-exciting current curve according to the recorded exciting current points, thereby generating a table between the motor torque points and the exciting current points and the torque current points.
Under the above circumstances, the first corresponding relationship is a table for recording excitation current points corresponding to each motor torque point under a fixed torque step length; step S2, including: obtaining exciting current points corresponding to two motor torque points adjacent to the required torque in a first corresponding relation; and linearly weighting the two exciting current points to obtain target exciting current. If the required torque is 15, two motor torque points adjacent to the required torque are respectively 10 and 20, and the exciting current points corresponding to the two exciting current points 10 and 20 are weighted linearly to obtain the target exciting current. If the required torque is 20, the weight of the motor torque point 20 corresponding to the excitation current point is set to 1, and the weight of the motor torque point 10 or 30 corresponding to the excitation current point is set to 0.
In the above case, the second correspondence is a table recording torque current points corresponding to each exciting current point; step S3, including: acquiring torque current points corresponding to two excitation current points adjacent to the target excitation current in the second corresponding relation; and linearly weighting the two torque current points to obtain target torque current.
After the target exciting current and the target torque current are obtained, the asynchronous motor is controlled according to the target exciting current and the target torque current, and the operation efficiency of the asynchronous motor can be improved. According to the embodiment of the invention, the coupling relation between the stator inductance and the exciting current is obtained through calibration, the coupling relation between the stator inductance and the exciting current is tied into a motor torque equation, so that a more accurate unitary quadratic equation between motor torque, exciting current and torque current is obtained, on the basis, a dominant expression between the torque current and the exciting current and an expression between the extremum torque and the exciting current when the motor torque takes the extremum under any current vector are obtained through a Lagrangian extremum method, and the process does not need to obtain specific motor parameters or rely on a large number of calibration points, so that the calibration workload is reduced; by searching the exciting current value under the equal torque step length on the curve of the extremum torque and the exciting current and searching the corresponding torque current value on the curve of the optimal torque current and the exciting current according to the exciting current value, the optimal control current corresponding to the required torque can be rapidly obtained, the calibration workload of the whole process is very small, the coupling relation is fully considered, and the calibration precision is high.
As shown in fig. 4, an embodiment of the present invention further provides an asynchronous motor current determining device, including:
the acquisition module is used for acquiring the required torque of the asynchronous motor;
the determining module is used for determining a target exciting current corresponding to the required torque according to a first corresponding relation between the motor torque and the exciting current;
and determining a target torque current corresponding to the target exciting current according to a second corresponding relation between the exciting current and the torque current.
Before the obtaining module obtains the required torque of the asynchronous motor, the embodiment of the invention also needs to establish the first corresponding relation and the second corresponding relation in advance, so that the current determining device of the asynchronous motor further comprises:
the building module is used for obtaining stator Q-axis voltages corresponding to a plurality of different exciting currents; calculating a stator inductance corresponding to each exciting current according to the Q-axis voltage of each stator and the corresponding exciting current; establishing a first expression of the stator inductance and the exciting current according to the plurality of stator inductances and the corresponding exciting currents; establishing a second expression of motor torque, exciting current and torque current according to the first expression; obtaining an extremum function expression of the second expression; the extremum function expression is made dominant, and a third expression of the torque current and the exciting current is obtained; obtaining a motor torque-exciting current curve according to the second expression and the third expression; establishing a first corresponding relation according to a motor torque-exciting current curve; and establishing a second corresponding relation according to the third expression.
The speed difference of the asynchronous motor is given as 0, the torque current is given as 0, the exciting current isd is given by a fixed step length isd_step, and the stator Q axis voltage Usq corresponding to each exciting current isd is recorded.
U Sq ＝ω·L s ·i sd ω is the stator current frequency and Ls is the stator inductance. Calculating to obtain stator inductances Ls corresponding to different exciting currents isd according to the previous formula; fitting a plurality of data points (isd, ls) on Matlab yields the curve equation ls=f (isd) of Ls and isd, i.e. the first expression.
The present invention provides two first expressions:
first, the first expression is a Fourier expression,a0, a1, a2, a3, b1, b3, w are fourier expression coefficients;
the second, the first expression is a polynomial expression,p1, p2, p3 are polynomial expression coefficients.
The asynchronous motor torque is related to motor inductance parameters, exciting current and torque current, wherein the inductance parameters are related to the exciting current, so that the motor torque and the exciting current are not in simple primary relation, and the relation between the inductance parameters and the exciting current is required to be reacted into the motor torque.
Approximately equalizing the stator leakage inductance and the rotor leakage inductance, and enabling:
L σs ＝α·L s ，L σs the stator leakage inductance is alpha, and the proportion coefficient of the stator leakage inductance and the stator inductance is alpha;
the torque expression may be converted to:
i.e.The second expression, T is motor torque, N p For the motor pole pair number, isq is the torque current.
And (3) solving an extremum function expression of motor torque relative to isd and isq binary functions under the additional condition of a fixed current vector by utilizing a Lagrange extremum method, wherein the additional condition is as follows:
i s vector current for the motor;
the Lagrangian auxiliary function is:
gamma is the Lagrangian multiplier;
the auxiliary function H deflects isd and isq and makes them equal to 0, so as to obtain:
and the two equations are combined to obtain an extremum function expression:
is the derivative of Ls with respect to isd;
if the first expression is a Fourier expression, then
And dominating the extremum function expression by Matlab:
syms isd isq a0 a1 a2 a3 b1 b2 b3 w
a third expression is obtained:
in the embodiment of the present invention, a0= 0.001733, a1= -0.0003476, b1= -0.002001, a2= -0.0008352, b2= 0.0004825, a3= 0.0001485, b3=0.0001686, and w= 0.006981 may be selected, and α is taken as an empirical value of 0.95.
If the first expression is a polynomial expression, a third expression may be obtained:
in the embodiment of the present invention, p1= -5.098, p2=4784, p3=4.798e+04 may be selected. The first expression is a polynomial expression, the derivative process would be very simple, but the fitting accuracy is slightly worse than the fourier one.
After the second expression and the third expression are obtained, a motor torque-exciting current curve can be further obtained according to the second expression and the third expression, as shown in fig. 2.
According to the embodiment of the invention, the expression of the motor torque-exciting current curve can be directly used as a first corresponding relation, and the third expression is used as a second corresponding relation, so that after the required torque of the asynchronous motor is obtained, the required torque can be input into the expression of the motor torque-exciting current curve to obtain the target exciting current, and the target exciting current is input into the third expression to obtain the target torque current, but the realization is difficult in practice.
Here, a motor torque-exciting current curve and a torque current-exciting current curve corresponding to the third expression may be respectively drawn in MATLAB, as shown in fig. 3, a fixed torque step (e.g. 10 n.m) is set, exciting current points under each motor torque point are found and recorded on the motor torque-exciting current curve, and torque current points under each exciting current point are found and recorded on the torque current-exciting current curve according to the recorded exciting current points, thereby generating a table between the motor torque points and the exciting current points and the torque current points.
Under the above circumstances, the first corresponding relationship is a table for recording excitation current points corresponding to each motor torque point under a fixed torque step length; the determining module may be further configured to: obtaining exciting current points corresponding to two motor torque points adjacent to the required torque in a first corresponding relation; and linearly weighting the two exciting current points to obtain target exciting current. If the required torque is 15, two motor torque points adjacent to the required torque are respectively 10 and 20, and the exciting current points corresponding to the two exciting current points 10 and 20 are weighted linearly to obtain the target exciting current. If the required torque is 20, the weight of the motor torque point 20 corresponding to the excitation current point is set to 1, and the weight of the motor torque point 10 or 30 corresponding to the excitation current point is set to 0.
In the above case, the second correspondence is a table recording torque current points corresponding to each exciting current point; the determining module may be further configured to: acquiring torque current points corresponding to two excitation current points adjacent to the target excitation current in the second corresponding relation; and linearly weighting the two torque current points to obtain target torque current.
After the target exciting current and the target torque current are obtained, the asynchronous motor is controlled according to the target exciting current and the target torque current, and the operation efficiency of the asynchronous motor can be improved. According to the embodiment of the invention, the coupling relation between the stator inductance and the exciting current is obtained through calibration, the coupling relation between the stator inductance and the exciting current is tied into a motor torque equation, so that a more accurate unitary quadratic equation between motor torque, exciting current and torque current is obtained, on the basis, a dominant expression between the torque current and the exciting current and an expression between the extremum torque and the exciting current when the motor torque takes the extremum under any current vector are obtained through a Lagrangian extremum method, and the process does not need to obtain specific motor parameters or rely on a large number of calibration points, so that the calibration workload is reduced; by searching the exciting current value under the equal torque step length on the curve of the extremum torque and the exciting current and searching the corresponding torque current value on the curve of the optimal torque current and the exciting current according to the exciting current value, the optimal control current corresponding to the required torque can be rapidly obtained, the calibration workload of the whole process is very small, the coupling relation is fully considered, and the calibration precision is high.
Based on the same inventive concept as the asynchronous motor current determination method described above, the embodiment of the invention further provides an electronic device, which comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, wherein the processor implements the steps of any one of the asynchronous motor current determination methods described above when executing the computer program.
Where a bus architecture (represented by a bus), a bus may comprise any number of interconnected buses and bridges, linking together various circuits, including one or more processors, as represented by a processor, and a memory, as represented by a memory. The bus may also link together various other circuits such as peripheral devices, voltage regulators, power management circuits, etc., as are well known in the art and, therefore, will not be further described herein. The bus interface provides an interface between the bus and the receiver and transmitter. The receiver and the transmitter may be the same element, i.e. a transceiver, providing a unit for communicating with various other apparatus over a transmission medium. The processor is responsible for managing the bus and general processing, while the memory may be used to store data used by the processor in performing operations.
Since the electronic device described in the embodiment of the present invention is an electronic device used to implement the method for determining an asynchronous motor current in the embodiment of the present invention, based on the method for determining an asynchronous motor current described in the embodiment of the present invention, those skilled in the art can understand the specific implementation manner of the electronic device and various modifications thereof, so how the electronic device implements the method in the embodiment of the present invention will not be described in detail herein. Any electronic device used by those skilled in the art to implement the method for determining current of an asynchronous motor according to the embodiments of the present invention falls within the scope of the present invention.
Based on the same inventive concept as the above-described asynchronous motor current determination method, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which when executed by a processor, implements any of the above-described asynchronous motor current determination methods.
It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (10)
1. A method for determining current of an asynchronous motor, comprising:
acquiring a required torque of an asynchronous motor;
determining a target exciting current corresponding to the required torque according to a first corresponding relation between the motor torque and the exciting current;
and determining a target torque current corresponding to the target exciting current according to a second corresponding relation between the exciting current and the torque current.
2. The method for determining the current of the asynchronous motor according to claim 1, wherein the first correspondence is a table recording excitation current points corresponding to each motor torque point at a fixed torque step;
the determining the target exciting current corresponding to the required torque according to the first corresponding relation between the motor torque and the exciting current comprises the following steps:
and obtaining the exciting current points corresponding to the two motor torque points adjacent to the required torque in the first corresponding relation, and carrying out linear weighting on the two exciting current points to obtain the target exciting current.
3. The asynchronous motor current determination method according to claim 1, wherein the second correspondence is a table recording torque current points corresponding to each of the exciting current points;
the determining the target torque current corresponding to the target exciting current according to the second corresponding relation between the exciting current and the torque current comprises:
acquiring the torque current points corresponding to two exciting current points adjacent to the target exciting current in the second corresponding relation;
and linearly weighting the two torque current points to obtain the target torque current.
4. The method for determining the current of an asynchronous motor according to claim 1, wherein before the step of obtaining the required torque of the asynchronous motor, further comprises:
establishing a first expression of stator inductance and the exciting current;
establishing a second expression of the motor torque, the exciting current and the torque current according to the first expression;
obtaining an extremum function expression of the second expression;
dominating the extremum function expression to obtain a third expression of the torque current and the exciting current;
obtaining a motor torque-exciting current curve according to the second expression and the third expression; establishing the first corresponding relation according to the motor torque-exciting current curve;
and establishing the second corresponding relation according to the third expression.
5. The asynchronous motor current determining method according to claim 4, wherein the second expression is:
t is the torque of the motor, N p Is the pole pair number of the motor, alpha is the proportional coefficient of the leakage inductance of the stator and the inductance of the stator, and f (i) sd ) For the first expression, isd is the excitation current, and isq is the torque current.
6. The asynchronous motor current determination method according to claim 5, wherein the third expression is:
or (b)
h(i sd )＝isd*(a0+a1*cos(isd*w)+a2*cos(2*isd*w)+a3*cos(3*isd*w)+b1*sin(isd*w)+b2*sin(2*isd*w)+b3*sin(3；*isd*w)
g(i sd )＝b1*isd*w*cos(isd*w)+2*b2*isd*w*cos(2*isd*w)+3*b3*isd*w*cos(3*isd*w)-a1*isd*w*sin(isd*w)-2*a2；*isd*w*sin(2*isd*w)-3*a3*isd*w*sin(3*isd*w)
a0, a1, a2, a3, b1, b2, b3, w are fourier expression coefficients;
p1, p2, p3 are polynomial expression coefficients.
7. The method of determining an asynchronous motor current according to claim 4, wherein before establishing the first expression of the stator inductance and the exciting current, further comprising:
acquiring a plurality of different stator Q-axis voltages corresponding to the exciting currents;
calculating the stator inductance corresponding to each exciting current according to the Q-axis voltage of each stator and the corresponding exciting current;
and establishing the first expression according to a plurality of stator inductances and the corresponding exciting currents.
8. An asynchronous motor current determining device, comprising:
the acquisition module is used for acquiring the required torque of the asynchronous motor;
the determining module is used for determining a target exciting current corresponding to the required torque according to a first corresponding relation between the motor torque and the exciting current;
and determining a target torque current corresponding to the target exciting current according to a second corresponding relation between the exciting current and the torque current.
9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the asynchronous motor current determination method of any of claims 1-7 when the computer program is executed.
10. A computer readable storage medium, characterized in that the computer readable storage medium has stored thereon a computer program which, when executed by a processor, implements the asynchronous motor current determination method of any of claims 1-7.
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