CN112234899B - Method and system for setting prediction step length of permanent magnet synchronous motor model - Google Patents

Method and system for setting prediction step length of permanent magnet synchronous motor model Download PDF

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CN112234899B
CN112234899B CN202011180791.2A CN202011180791A CN112234899B CN 112234899 B CN112234899 B CN 112234899B CN 202011180791 A CN202011180791 A CN 202011180791A CN 112234899 B CN112234899 B CN 112234899B
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motor
step length
stator
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setting
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CN112234899A (en
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陈曦
牛峰
李奎
方攸同
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Hebei University of Technology
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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
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
    • 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
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/22—Current control, e.g. using a current control loop
    • 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
    • H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
    • H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
    • H02P25/022—Synchronous motors
    • 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
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/34—Modelling or simulation for control purposes

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Abstract

The invention provides a method and a system for setting a prediction step length of a permanent magnet synchronous motor model, wherein the method for setting the prediction step length of the permanent magnet synchronous motor model comprises the following steps: establishing a stator current state equation of the motor under a d-q rotating coordinate system; discretizing a stator current state equation to obtain a motor stator current prediction model; judging the working condition of the motor, and setting the predicted step length according to different working conditions; predicting d-axis and q-axis currents by taking qTs as step length according to the stator current prediction model to obtain a prediction result; and evaluating the prediction results of the d-axis current and the q-axis current by adopting a cost function, selecting the voltage vector with the minimum average error as an optimal voltage vector and outputting the optimal voltage vector in the next control period. The step length prediction method improves the prediction precision of the step length in the prediction current control and reduces the operation amount. The prediction step length setting system of the permanent magnet synchronous motor model provided by the invention applies the prediction step length method.

Description

Method and system for setting prediction step length of permanent magnet synchronous motor model
Technical Field
The invention relates to the technical field of motors, in particular to a method and a system for setting a prediction step length of a permanent magnet synchronous motor model.
Background
In the high-performance permanent magnet synchronous motor Control method, Model Predictive Current Control (MPCC) is widely paid attention to due to the advantages of simple principle, easy handling of nonlinear constraints and the like. When the total prediction duration in the prediction control method is fixed, the prediction step length is a key factor influencing the prediction error and the arithmetic operation amount, and theoretical analysis and experimental tests show that the shorter the prediction step length is, the smaller the prediction error is. However, due to the limitation of hardware computing resources, the prediction step size cannot be infinitely shortened, and therefore, how to determine the prediction step size is a problem to be studied. The prediction step length and the control period in the traditional prediction current control method are the same, and the prediction precision and the algorithm operand of the MPCC method are difficult to flexibly balance.
Disclosure of Invention
The invention aims to provide a method and a system for setting a prediction step length of a permanent magnet synchronous motor model, so as to improve the prediction precision of the step length in prediction current control and reduce the calculation amount.
In order to achieve the above purpose, the invention provides the following technical scheme:
the invention provides a method for setting a prediction step length of a permanent magnet synchronous motor model, which comprises the following steps of: establishing a stator current state equation of the motor under a d-q rotating coordinate system; discretizing a stator current state equation to obtain a motor stator current prediction model; judging the working condition of the motor, and setting the predicted step length according to different working conditions; predicting d-axis and q-axis currents by taking qTs as step length according to the stator current prediction model to obtain a prediction result; and evaluating the prediction results of the d-axis current and the q-axis current by adopting a cost function, selecting the voltage vector with the minimum average error as an optimal voltage vector and outputting the optimal voltage vector in the next control period.
Compared with the prior art, the method for setting the prediction step length of the permanent magnet synchronous motor model determines the prediction step length according to the operation condition of the motor, can balance the prediction precision and the algorithm operand of the motor during transient and steady operation, and can improve the prediction precision and the following performance of the motor during transient operation while ensuring the steady performance of a system.
Optionally, the stator current state equation of the motor in the d-q rotating coordinate system is as follows:
Figure BDA0002750113470000011
Figure BDA0002750113470000021
wherein id、iqD-axis current and q-axis current of the stator respectively; u. ofd、uqThe voltages of d and q axes of the stator are respectively; l isd、LqThe inductors of the d axis and the q axis of the stator are respectively; rsIs a stator resistor; omegarIs the rotor electrical angular velocity; psifIs a rotor permanent magnet flux linkage.
Optionally, the motor stator current prediction model is as follows:
Figure BDA0002750113470000022
Figure BDA0002750113470000023
wherein id、iqD-axis current and q-axis current of the stator respectively; u. ofd、uqThe voltages of d and q axes of the stator are respectively; l isd、LqThe inductors of the d axis and the q axis of the stator are respectively; rsIs a stator resistor; omegarIs the rotor electrical angular velocity; psifIs a rotor permanent magnet flux linkage; q is a setting coefficient, z/N is defined as q, N is a prediction step number, z is an integer, and the value range of q is (0, z]。
Optionally, the determining the working condition of the motor and setting the predicted step length according to different working conditions includes:
when the working condition of the motor is judged to be a steady state, the predicted step length setting coefficient is q2And q is2≥1；
When the working condition of the motor is judged to be transient and the given rotating speed of the motor changes, the predicted step length setting coefficient is as follows:
Figure BDA0002750113470000024
wherein q is0Setting a coefficient for the minimum prediction step length, q1Setting coefficient, delta omega, for the longest predicted step length in the transient processmaxIs the maximum value of Δ ω;
when the working condition of the motor is judged to be transient and the load of the motor changes, the predicted step length setting coefficient is as follows:
Figure BDA0002750113470000025
wherein R isωmaxThe maximum value of the absolute value of the change rate of the rotating speed after the load of the motor is changed.
The invention also provides a system for setting the prediction step length of the permanent magnet synchronous motor model, which comprises the following steps: the establishing module is used for establishing a stator current state equation of the motor under a d-q rotating coordinate system; the stator current prediction model module is used for discretizing a stator current state equation to obtain a motor stator current prediction model; the judging module is used for judging the working condition of the motor and setting the predicted step length according to different working conditions; the prediction module is used for predicting the d-axis current and the q-axis current by taking qTs as step length according to the stator current prediction model to obtain a prediction result; and the evaluation module is used for evaluating the prediction results of the d-axis current and the q-axis current by adopting a cost function, selecting the voltage vector with the minimum average error as an optimal voltage vector and outputting the optimal voltage vector in the next control period.
Compared with the prior art, the beneficial effect of the prediction step length setting system of the permanent magnet synchronous motor model is the same as that of the prediction step length setting method of the permanent magnet synchronous motor model, and the description is omitted here.
Optionally, the stator current state equation of the motor in the d-q rotating coordinate system is as follows:
Figure BDA0002750113470000031
Figure BDA0002750113470000032
wherein id、iqD-axis current and q-axis current of the stator respectively; u. ofd、uqThe voltages of d and q axes of the stator are respectively; l isd、LqThe inductors of the d axis and the q axis of the stator are respectively; rsIs a stator resistor; omegarIs the rotor electrical angular velocity; psifIs a rotor permanent magnet flux linkage.
Optionally, the motor stator current prediction model is as follows:
Figure BDA0002750113470000033
Figure BDA0002750113470000034
wherein id、iqD-axis current and q-axis current of the stator respectively; u. ofd、uqThe voltages of d and q axes of the stator are respectively; l isd、LqThe inductors of the d axis and the q axis of the stator are respectively; rsIs a stator resistor; omegarIs the rotor electrical angular velocity; psifIs a rotor permanent magnet flux linkage; q is a setting coefficient, z/N is defined as q, N is a prediction step number, z is an integer, and the value range of q is (0, z]。
Optionally, the determining module includes:
a first judging unit for predicting that the setting coefficient of the step length is q when the working condition of the motor is judged to be a steady state2And q is2≥1；
And the second judgment unit is used for predicting the step length setting coefficient to be as follows when the working condition of the motor is judged to be a transient state and the given rotating speed of the motor changes:
Figure BDA0002750113470000035
wherein q is0Setting a coefficient for the minimum prediction step length, q1Setting coefficient, delta omega, for the longest predicted step length in the transient processmaxIs the maximum value of Δ ω;
and the third judging unit is used for predicting the step length setting coefficient to be:
Figure BDA0002750113470000036
wherein R isωmaxThe maximum value of the absolute value of the change rate of the rotating speed after the load of the motor is changed.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a flowchart of a method for setting a predicted step size of a permanent magnet synchronous motor model according to an embodiment of the present invention;
fig. 2 is a schematic diagram of an actual gear adjustment of a predicted step size of a permanent magnet synchronous motor model according to an embodiment of the present invention;
fig. 3 is a schematic diagram illustrating an actual gear adjustment of a predicted step size of a permanent magnet synchronous motor model according to another embodiment of the present invention;
fig. 4 is a block diagram of a predicted step length setting system of a permanent magnet synchronous motor model according to an embodiment of the present invention;
fig. 5 is a block diagram of a system for setting a predicted step size of a permanent magnet synchronous motor model according to another embodiment of the present invention.
Reference numerals:
100. the device comprises an establishing module, 200, a stator current prediction model module, 300, a judging module, 400, a prediction module, 500, an evaluation module, 3001, a first judging unit, 3002, a second judging unit and 3003, and a third judging unit.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, as used herein, refer to an orientation or positional relationship indicated in the drawings, which is solely for the purpose of facilitating the description and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and is therefore not to be construed as limiting the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In a high-performance permanent magnet synchronous motor Control method, a Model Predictive Current Control (MPCC) is widely paid attention to due to advantages of simple principle, easy handling of nonlinear constraints and the like. When the total prediction duration in the prediction control method is fixed, the prediction step length is a key factor influencing the prediction error and the arithmetic operation amount, and theoretical analysis and experimental tests show that the shorter the prediction step length is, the smaller the prediction error is. However, due to the limitation of hardware computing resources, the prediction step size cannot be infinitely shortened, and therefore, how to determine the prediction step size is a problem to be studied. The prediction step length and the control period in the traditional prediction current control method are the same, and the prediction precision and the algorithm operand of the MPCC method are difficult to flexibly balance.
In view of the above problem, as shown in fig. 1, an embodiment of the present invention provides a method for setting a predicted step size of a permanent magnet synchronous motor model, including the following steps:
s100, establishing a stator current state equation of the motor in a d-q rotating coordinate system.
A permanent-magnet synchronous motor (PMSM) is called as PMSM for short, and the embodiment of the present invention is mainly directed to the above-described motor.
In one possible implementation, the stator current state equation of the motor in the d-q rotating coordinate system is as follows:
Figure BDA0002750113470000051
Figure BDA0002750113470000052
wherein id、iqD-axis current and q-axis current of the stator respectively; u. ofd、uqThe voltages of d and q axes of the stator are respectively; l isd、LqThe inductors of the d axis and the q axis of the stator are respectively; rsIs a stator resistor; omegarIs the rotor electrical angular velocity; psifIs a rotor permanent magnet flux linkage.
S200, discretizing a stator current state equation to obtain a motor stator current prediction model.
Discretizing a continuous state equation of the stator current according to a first-order forward Euler discretization method to obtain a stator current prediction model as follows:
Figure BDA0002750113470000053
Figure BDA0002750113470000054
wherein id、iqD-axis current and q-axis current of the stator respectively; u. ofd、uqThe voltages of d and q axes of the stator are respectively; l isd、LqThe inductors of the d axis and the q axis of the stator are respectively; rsIs a stator resistor; omegarIs the rotor electrical angular velocity; psifIs a rotor permanent magnet flux linkage; q is a setting coefficient, z/N is defined as q, N is a prediction step number, z is an integer, and the value range of q is (0, z]。
The stator current prediction model predicts d and q axis currents in steps qTs. When 0< q <1, the prediction step is smaller than the control period Ts; when q is equal to 1, the prediction step length is equal to the control period, and the method is equivalent to the traditional single-step MPCC method; when 1< q ≦ N, the prediction step size is greater than Ts. The relationship between the prediction step length and the duration of the control period is adjusted by adjusting the q value, the prediction precision and the algorithm calculated amount are balanced, and the control requirements under different operation conditions are met.
S300, judging the working condition of the motor, and setting the predicted step length according to different working conditions.
When the working condition of the motor is judged, the change of the given rotating speed and the change of the load are divided.
When the given rotating speed of the motor changes, the difference value delta omega between the given rotating speed and the actual rotating speed is
Figure BDA0002750113470000061
In the formula, ωmGiven speed of rotation, ω, of the motormAnd when the delta omega exceeds a certain range, the given rotating speed of the motor is judged to be changed, and the system is in a transient operation process. Considering that the rotating speed of the motor in normal operation fluctuates, a hysteresis comparison link is required to be arranged to prevent misjudgment. The upper and lower thresholds of the hysteresis comparator are respectively delta omega2And Δ ω1。
When the load of the motor changes, the rotating speed of the motor fluctuates by a certain amplitude, and the absolute value R of the rotating speed change rate can be adoptedωDetermining a change in load
Figure BDA0002750113470000062
In the formula, Ts is a control period, omegam-kMotor speed before k cycles, RωThe magnitude of (a) reflects the rate of change of the motor speed within a certain time. When R isωWhen the load of the motor is over a certain threshold, the change of the load of the motor is judged. In order to prevent misjudgment caused by rotation speed fluctuation when the motor normally operates, a hysteresis comparator is also adopted for judging load change. The upper and lower thresholds of the hysteresis comparator are set to R respectivelyω2And Rω1。
S400, predicting d-axis and q-axis currents by taking qTs as step length according to the stator current prediction model to obtain a prediction result.
And after the judgment of the operation condition of the motor is finished, setting the predicted step length according to the current working condition. When the motor is in a steady state, the predicted step length setting coefficient is q2，q2Not less than 1. When the given rotating speed of the motor changes, the predicted step length setting coefficient is
Figure BDA0002750113470000063
In the formula, q0The minimum prediction step length setting coefficient can be set according to the limit calculation capacity of the processor. q. q.s1Setting coefficient, delta omega, for the longest predicted step length in the transient processmaxIs the maximum value of Δ ω. The predicted step length setting coefficient can be changed at q along with the variable quantity of the given rotating speed of the motor0To q1The range is continuously adjustable.
In practical application, the system is unstable due to continuous switching of the predicted step length, so that the predicted step length setting coefficient is subjected to multi-gear adjustment, and the multi-gear adjustment principle of the predicted step length setting coefficient under given rotation speed change is shown in fig. 2. In FIG. 2The slope of (a) represents a continuously changing predicted step setting coefficient obtained when the given rotation speed changes. Less than Rω1Indicating that the motor is entering steady state, greater than Rω1Indicating an entering transient. q. q.s01、q02、q03Indicating the gear that is adjusted in the actual application. Of course, the number of gears can be determined according to actual conditions. Prediction step length setting coefficient in interval [ q0,q01) In time, a prediction step length setting coefficient is taken as q0(ii) a When the calculated prediction step setting coefficient is in the interval [ q ]01,q02) In time, a prediction step length setting coefficient is taken as q01And so on.
When the load of the motor changes, the predicted step length setting coefficient is
Figure BDA0002750113470000071
In the formula, RωmaxThe maximum value of the absolute value of the change rate of the rotating speed after the load of the motor is changed.
The calculated q is continuously variable, and the prediction step size of the MPCC method in practical application cannot be continuously adjustable. Therefore, in practical application, different gears can be set for the predicted step length setting coefficient, and gear adjustment can be performed according to the system operation condition. The principle of gear adjustment is shown in fig. 3. The slope in fig. 3 represents the continuously changing predicted step setting coefficient obtained when the motor load changes. Less than Rω1Indicating that the motor is entering steady state, greater than Rω1Indicating an entering transient. q. q.s01、q02、q03Indicating the gear that is adjusted in the actual application. Of course, the number of gears can be determined according to actual conditions. Prediction step length setting coefficient in interval [ q0,q01) In time, a prediction step length setting coefficient is taken as q0(ii) a When the calculated prediction step setting coefficient is in the interval [ q ]01,q02) In time, a prediction step length setting coefficient is taken as q01And so on.
And S500, evaluating the prediction results of the d-axis current and the q-axis current by adopting a cost function, selecting the voltage vector with the minimum average error as an optimal voltage vector and outputting the optimal voltage vector in the next control period.
In one possible implementation, the prediction of d and q-axis currents is evaluated using a cost function. The cost function is as follows:
Figure BDA0002750113470000072
in the formula idA and iqAnd the values are given values of d-axis current and q-axis current of the motor respectively. And (4) carrying out square operation and averaging processing on the error between the predicted value of each step of current and the given value under the action of each voltage vector, and finally selecting the voltage vector with the minimum average error as the optimal voltage vector and outputting the optimal voltage vector in the next control period.
Compared with the traditional single-step MPCC method, the prediction step length setting method of the permanent magnet synchronous motor model provided by the embodiment of the invention has the advantages of smaller transient/steady-state current prediction error and better current following performance. Meanwhile, the torque and flux linkage pulsation in a steady state are lower, and the steady-state control performance of the MPCC is improved.
As shown in fig. 4, an embodiment of the present invention further provides a system for setting a predicted step size of a permanent magnet synchronous motor model, including: the establishing module 100 is used for establishing a stator current state equation of the motor in a d-q rotating coordinate system; the stator current prediction model module 200 is used for discretizing a stator current state equation to obtain a motor stator current prediction model; and the judging module 300 is used for judging the working condition of the motor and setting the predicted step length according to different working conditions. The prediction module 400 is used for predicting the d-axis current and the q-axis current by taking qTs as a step length according to the stator current prediction model to obtain a prediction result; and the evaluation module 500 is configured to evaluate the prediction results of the d-axis current and the q-axis current by using a cost function, select a voltage vector with the minimum average error as an optimal voltage vector, and output the optimal voltage vector in the next control cycle.
As an alternative embodiment, the stator current state equation of the motor in the d-q rotation coordinate system is:
Figure BDA0002750113470000081
Figure BDA0002750113470000082
wherein id、iqD-axis current and q-axis current of the stator respectively; u. ofd、uqThe voltages of d and q axes of the stator are respectively; l isd、LqThe inductors of the d axis and the q axis of the stator are respectively; rsIs a stator resistor; omegarIs the rotor electrical angular velocity; psifIs a rotor permanent magnet flux linkage.
As an alternative embodiment, the motor stator current prediction model is:
Figure BDA0002750113470000083
Figure BDA0002750113470000084
wherein id、iqD-axis current and q-axis current of the stator respectively; u. ofd、uqThe voltages of d and q axes of the stator are respectively; l isd、LqThe inductors of the d axis and the q axis of the stator are respectively; rsIs a stator resistor; omegarIs the rotor electrical angular velocity; psifIs a rotor permanent magnet flux linkage; q is a setting coefficient, z/N is defined as q, N is a prediction step number, z is an integer, and the value range of q is (0, z]。
As an optional implementation manner, the determining module includes:
a first determination unit 3001, configured to predict that the step setting coefficient is q when determining that the operating condition of the motor is a steady state2And q is2≥1；
The second determination unit 3002 is configured to, when it is determined that the operating condition of the motor is a transient state and the given rotation speed of the motor changes, predict a step length setting coefficient as follows:
Figure BDA0002750113470000085
wherein q is0Setting a coefficient for the minimum prediction step length, q1Setting coefficient, delta omega, for the longest predicted step length in the transient processmaxIs the maximum value of Δ ω;
a third determining unit 3003, configured to, when it is determined that the operating condition of the motor is a transient state and the load of the motor changes, predict a step setting coefficient as follows:
Figure BDA0002750113470000086
wherein R isωmaxThe maximum value of the absolute value of the change rate of the rotating speed after the load of the motor is changed.
Compared with the traditional single-step MPCC method, the prediction error of the transient/steady-state current of the prediction step setting system of the permanent magnet synchronous motor model provided by the embodiment of the invention is smaller, and the current following performance is better. Meanwhile, the torque and flux linkage pulsation in a steady state are lower, and the steady-state control performance of the MPCC is improved.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (6)

1. A method for setting a prediction step length of a permanent magnet synchronous motor model is characterized by comprising the following steps: the method comprises the following steps:
establishing a stator current state equation of the motor under a d-q rotating coordinate system;
discretizing the stator current state equation to obtain a motor stator current prediction model;
judging the working condition of the motor, and setting the predicted step length according to different working conditions;
predicting d and q axis currents by taking qTs as a step length according to the stator current prediction model to obtain a prediction result, wherein q is a setting coefficient, and Ts is a control period;
evaluating the prediction results of the d-axis current and the q-axis current by adopting a cost function, selecting a voltage vector with the minimum average error as an optimal voltage vector and outputting the optimal voltage vector in the next control period;
the judging of the working condition of the motor and the setting of the predicted step length according to different working conditions comprise:
when the working condition of the motor is judged to be a steady state, the predicted step length setting coefficient is q2And q is2≥1；
When the working condition of the motor is judged to be transient and the given rotating speed of the motor changes, the predicted step length setting coefficient is as follows:
Figure FDA0003361076210000011
wherein q is0Setting a coefficient for the minimum prediction step length, q1Setting a coefficient for the longest predicted step length in the transient process, wherein delta omega is the difference between a given rotating speed and an actual rotating speed, and delta omega ismaxIs the maximum value of Δ ω;
when the working condition of the motor is judged to be transient and the load of the motor changes, the predicted step length setting coefficient is as follows:
Figure FDA0003361076210000012
wherein R isωmaxThe maximum value of the absolute value of the change rate of the rotating speed after the load of the motor is changed.
2. The method for setting the predicted step length of the permanent magnet synchronous motor model according to claim 1, characterized in that:
the stator current state equation of the motor in a d-q rotating coordinate system is as follows:
Figure FDA0003361076210000013
Figure FDA0003361076210000014
wherein id、iqD-axis current and q-axis current of the stator respectively; u. ofd、uqThe voltages of d and q axes of the stator are respectively; l isd、LqThe inductors of the d axis and the q axis of the stator are respectively; rsIs a stator resistor; omegarIs the rotor electrical angular velocity; psifIs a rotor permanent magnet flux linkage.
3. The method for setting the predicted step length of the permanent magnet synchronous motor model according to claim 1, characterized in that:
the motor stator current prediction model is as follows:
Figure FDA0003361076210000021
Figure FDA0003361076210000022
wherein id、iqD-axis current and q-axis current of the stator respectively; u. ofd、uqThe voltages of d and q axes of the stator are respectively; l isd、LqThe inductors of the d axis and the q axis of the stator are respectively; rsIs a stator resistor; omegarIs the rotor electrical angular velocity; psifIs a rotor permanent magnet flux linkage; q is a setting coefficient, z/N is defined as q, N is a prediction step number, z is an integer, and the value range of q is (0, z]。
4. A prediction step length setting system of a permanent magnet synchronous motor model is characterized in that: the method comprises the following steps:
the establishing module is used for establishing a stator current state equation of the motor under a d-q rotating coordinate system;
the stator current prediction model module is used for discretizing the stator current state equation to obtain a motor stator current prediction model;
the judging module is used for judging the working condition of the motor and setting the predicted step length according to different working conditions;
the prediction module is used for predicting d-axis and q-axis currents by using qTs as step length according to the stator current prediction model to obtain a prediction result, wherein q is a setting coefficient, and Ts is a control period;
the evaluation module is used for evaluating the prediction results of the d-axis current and the q-axis current by adopting a cost function, selecting a voltage vector with the minimum average error as an optimal voltage vector and outputting the optimal voltage vector in the next control period;
the judging module comprises:
a first judging unit, configured to, when it is judged that the operating condition of the motor is a steady state, set the predicted step size as q2And q is2≥1；
The second judgment unit is used for judging that the working condition of the motor is a transient state and the given rotating speed of the motor changes, and the predicted step length setting coefficient is as follows:
Figure FDA0003361076210000023
wherein q is0Setting a coefficient for the minimum prediction step length, q1Setting a coefficient for the longest predicted step length in the transient process, wherein delta omega is the difference between a given rotating speed and an actual rotating speed, and delta omega ismaxIs the maximum value of Δ ω;
a third judging unit, configured to, when it is judged that the operating condition of the motor is a transient state and the load of the motor changes, set the predicted step size coefficient as:
Figure FDA0003361076210000024
wherein R isωmaxThe maximum value of the absolute value of the change rate of the rotating speed after the load of the motor is changed.
5. The system for setting the predicted step length of the permanent magnet synchronous motor model according to claim 4, characterized in that:
the stator current state equation of the motor in a d-q rotating coordinate system is as follows:
Figure FDA0003361076210000031
Figure FDA0003361076210000032
wherein id、iqD-axis current and q-axis current of the stator respectively; u. ofd、uqThe voltages of d and q axes of the stator are respectively; l isd、LqThe inductors of the d axis and the q axis of the stator are respectively; rsIs a stator resistor; omegarIs the rotor electrical angular velocity; psifIs a rotor permanent magnet flux linkage.
6. The system for setting the predicted step length of the permanent magnet synchronous motor model according to claim 4, characterized in that:
the motor stator current prediction model is as follows:
Figure FDA0003361076210000033
Figure FDA0003361076210000034
wherein id、iqD-axis current and q-axis current of the stator respectively; u. ofd、uqAre respectively a statord. A q-axis voltage; l isd、LqThe inductors of the d axis and the q axis of the stator are respectively; rsIs a stator resistor; omegarIs the rotor electrical angular velocity; psifIs a rotor permanent magnet flux linkage; q is a setting coefficient, z/N is defined as q, N is a prediction step number, z is an integer, and the value range of q is (0, z]。
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