Motor electromagnetic torque equation based on vector magnetic circuit, maximum torque current ratio calculation method and control method

Abstract

The invention belongs to the technical field of motor control, and particularly discloses a vector magnetic circuit-based motor electromagnetic torque equation and maximum torque current ratio calculation method and control method.The method comprises the following steps of: firstly, establishing a vector magnetic circuit model of a permanent magnet motor, and representing the influence of eddy current and hysteresis effect in a magnetic material on the electromagnetic torque of the motor by using equivalent magnetic induction; establishing a permanent magnet motor vector magnetic circuit electromagnetic torque equation containing equivalent magnetic induction through coordinate transformation; and then, a maximum torque current ratio control method of the permanent magnet motor is further provided. According to the method provided by the invention, the influence of eddy current and hysteresis effect in a magnetic material on the electromagnetic torque of the motor is fully considered, and the torque control of the permanent magnet motor is more accurate through the maximum torque current ratio control.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor control, and in particular relates to a motor electromagnetic torque equation based on a vector magnetic circuit, a maximum torque current ratio calculation method and a control method. Background Art

[0002] Surface permanent magnet synchronous motor (SPMSM) has the advantages of simple structure, high power density, wide speed regulation range and high working efficiency. It is widely used in industries, electric vehicles, home appliances and other fields. The performance of SPMSM is not only affected by the structure of the motor itself, but also by the control algorithm. Vector control is one of the most common control methods of SPMSM. The vector control of AC motor refers to the fact that the excitation current and armature current of DC motor are perpendicular to each other and there is no coupling relationship between the two. Based on the Clark transformation and Park transformation in coordinate transformation theory, the three-phase stator current is decomposed into independent torque components (cross-axis current) and excitation components (direct-axis current), realizing the decoupling control of AC motor magnetic field and torque, so that AC motor has similar control performance to DC motor.

[0003] Professor Cheng Ming's team at Southeast University discovered the magnetic induction and magnetic capacitance phenomena in the magnetic circuit, established the vector magnetic circuit theory containing the three elements of magnetic resistance, magnetic induction and magnetic capacitance, and the magnetoelectric power law, and provided a new method for considering the iron loss of the motor, which is different from the equivalent resistance. The active loss caused by the magnetic induction element corresponds to the eddy current loss in the magnetic circuit, and the active loss caused by the magnetic capacitance element corresponds to the hysteresis loss in the magnetic circuit. By introducing magnetic induction and magnetic capacitance into the permanent magnet motor model, the influence of eddy current effect and hysteresis effect on the permanent magnet magnetic flux and the stator magnetic flux excited by the armature current can be considered. Based on the vector magnetic circuit theory, a new permanent magnet motor control mathematical model can be established. Since the model considers both the magnetic circuit and the circuit, the introduction of iron loss is more reasonable. However, in the traditional control method, the magnetomotive force and magnetic flux of the motor are in phase, and the influence of eddy current and hysteresis effect on the motor control performance is not considered. Summary of the invention

[0004] The purpose of the present invention is to propose an electromagnetic torque equation of a motor based on a vector magnetic circuit, so that the modeling of the permanent magnet motor is more accurate and the calculation of the electromagnetic torque is more precise; the iron loss angle is used to characterize the magnetomotive force and the flux phase difference caused by the iron loss, and the influence of eddy current and hysteresis effects in the magnetic material on the electromagnetic torque of the motor is fully considered.

[0005] The present invention proposes an electromagnetic torque equation for a surface-mounted permanent magnet motor based on a vector magnetic circuit. The electromagnetic torque equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit considering the eddy current and hysteresis effects in the coordinate system is expressed as follows: (1) in, and for In the coordinate system Shaft current and Shaft current, for The inductance in the coordinate system, is the permanent magnet flux, is the number of motor pole pairs, is the iron loss angle, for Electromagnetic torque of surface-mounted permanent magnet motor based on vector magnetic circuit considering eddy current and hysteresis effects in coordinate system.

[0006] Based on the electromagnetic torque equation of the surface-mounted permanent magnet motor of the present invention, the present invention also proposes a method for calculating the maximum torque current ratio of the surface-mounted permanent magnet motor based on a vector magnetic circuit. The electromagnetic torque equation of the surface-mounted permanent magnet motor includes Shaft current component and Shaft current component Therefore, it is necessary to find the optimal combination of quadrature and direct axis currents under the current operating state to obtain the maximum torque current ratio. The expression is as follows: (2) The relationship between the stator current vector and the quadrature and direct axis currents is expressed as: (3) in, and for In the coordinate system Shaft current and Shaft current, for The stator current vector in the coordinate system is: is the stator current vector angle, is the stator current vector and The angle of the axis, is the permanent magnet flux, is the number of motor pole pairs, is the iron loss angle.

[0007] Furthermore, substituting equation (3) into the electromagnetic torque equation of equation (2), we obtain the electromagnetic torque The stator current vector angle The relationship is:

[0008] T d = 3 2 p n [ 1 2 L s i s 2 sin 2 d + ψ f cos 2 d ( i s sin β ) + 1 2 ψ f sin 2 d ( i s cos β )] (4)

[0009] Stator current vector Perform phase shift processing to obtain the unit current electromagnetic torque The expression is:

[0010] (5)

[0011] When the derivative of the unit current electromagnetic torque with respect to the stator current vector angle is equal to zero, the unit current electromagnetic torque reaches a maximum value. At this time, the motor operating point corresponding to the stator current vector angle is the MTPA control point, which is specifically expressed as the unit current electromagnetic torque The maximum relationship needs to be satisfied:

[0012] (6)

[0013] Further, we obtain:

[0014] (7)

[0015] Furthermore, in the surface mounted permanent magnet motor Axis and Two vector magnetic circuit parameters, magnetic induction L and magnetic capacitance C, are introduced into the axial vector magnetic circuit model. Both magnetic induction L and magnetic capacitance C make the magnetic flux lag behind the magnetomotive force or current. The angle at which the magnetic flux lags behind the magnetomotive force or current is the iron loss angle. , expressed as:

[0016] (8)

[0017] make

[0018] (9)

[0019] say is the equivalent magnetic induction parameter;

[0020] Since the magnetic resistance is expressed as , iron loss angle of surface mounted permanent magnet motor It is expressed as:

[0021] (3)

[0022] L is The magnetic induction in the coordinate system, C is Magnetic capacitance in the coordinate system, L eq for The equivalent magnetic induction in the coordinate system is, for The magnetic resistance in the coordinate system, for The inductance in the coordinate system, is the equivalent magnetic induction coefficient, is the iron loss angle, is the rotor electrical angular velocity, is the number of turns of the armature winding.

[0023] Furthermore, the voltage equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit is:

[0024] [ u R u L ] = [ R s cos d + pL s cos d − oh L s cos d oh L s cos d R s cos d + pL s cos d ] [ i d i q ] + [ 0 oops f cos d ] (9)

[0025] in, and is the voltage in the RL coordinate system, and for The current in the coordinate system, for The inductance in the coordinate system, for The resistance in the coordinate system, is the permanent magnet flux, is the iron loss angle, is the electrical angular velocity of the rotor, is the differential operator.

[0026] The voltage in the RL coordinate system is The voltage relationship in the coordinate system is as follows:

[0027] [ u R u L ] = M d [ u d u q ] (10)

[0028] in, is the coordinate transformation matrix, expressed as:

[0029] M d = [ cos d − sin d sin d cos d ] (11)

[0030] The present invention also proposes a surface mounted permanent magnet motor control method based on a vector magnetic circuit, comprising the following steps:

[0031] Sampling the three-phase current of the surface-mounted permanent magnet motor to obtain the sampled value , , ,Will , , After coordinate transformation, we get Current sampling value in the coordinate system and ;

[0032] Rotor electrical angular velocity and the rotor electrical angular velocity setting value The error is obtained by PI controller to obtain the stator current vector , obtained through the relationship between the stator current vector and the quadrature and direct axis currents Axis and Shaft current setting value and , specifically:

[0033]

[0034]

[0035]

[0036] represents the stator current vector angle, represents the iron loss angle;

[0037] Will Current sampling value in the coordinate system and With the set value and The error is input into two PI controllers respectively to obtain the voltage setting value in the RL coordinate system and ,Will and Through the coordinate transformation matrix The inverse transformation yields Voltage setting value in coordinate system and , through the inverse Park transform, and then Voltage setting value in coordinate system and Transformation Voltage setting value in coordinate system and ,use and The synthesized voltage space vector is input into the voltage space vector modulation module for modulation, and the state coding values ​​of the three half bridges are output to control the MOS tube switches of the three-phase inverter to control the motor.

[0038] Furthermore, the stator current vector angle in the present invention is The corresponding motor operating point is the MTPA control point.

[0039] Compared with the traditional electromagnetic torque equation and control method, the electromagnetic torque equation and control method of the present invention have the following beneficial effects:

[0040] (1) The maximum torque current ratio control method proposed by the present invention based on the electromagnetic torque equation of the vector magnetic circuit makes the torque output of the permanent magnet motor maximum under this control method. The control method has higher torque utilization and makes the torque control of the permanent magnet motor more precise;

[0041] (2) The present invention proposes an electromagnetic torque equation for a surface-mounted permanent magnet motor based on a vector magnetic circuit, which solves the problem of inconsistency between the calculated value and the actual measured value of the electromagnetic torque of the motor under actual operating conditions. This is of great significance for the design of the motor and numerical calculations in actual engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly and intuitively understand the relevant principles of the present invention, the following figures are attached for easy understanding.

[0043] Figure 1 is the RL coordinate system established in the present invention and Schematic diagram of coordinate system relationship.

[0044] Figure 2 is the d-axis current in the maximum torque current ratio , q-axis current With the stator current vector Schematic diagram of the relationship.

[0045] Figure 3 It is a block diagram of the maximum torque-current ratio control method of the surface-mounted permanent magnet motor based on the vector magnetic circuit in the present invention.

[0046] FIG4( a ) is a diagram showing the d-axis current simulation effect obtained by using the control method of the present invention when the motor speed is 1500 r / min.

[0047] FIG4( b ) is a diagram showing the d-axis current simulation effect obtained by using a traditional vector control method when the motor speed is 1500 r / min in the present invention.

[0048] FIG4( c ) is a simulation effect diagram of the difference in d-axis current obtained by using the control method of the present invention and the traditional vector control method when the motor speed is 1500 r / min.

[0049] FIG5( a ) is a diagram showing the simulation effect of the q-axis current obtained by using the control method of the present invention when the motor speed is 1500 r / min.

[0050] FIG5( b ) is a diagram showing the simulation effect of the q-axis current obtained by using a traditional vector control method when the motor speed is 1500 r / min in the present invention.

[0051] FIG5(c) is a simulation effect diagram of the difference in q-axis current obtained by using the control method of the present invention and the traditional vector control method when the motor speed is 1500 r / min.

[0052] FIG6( a ) is a diagram showing a simulation effect of the torque-to-current ratio obtained by using the control method of the present invention when the motor speed is 1500 r / min.

[0053] FIG6( b ) is a diagram showing the simulation effect of the torque-to-current ratio obtained by using a traditional vector control method when the motor speed is 1500 r / min in the present invention.

[0054] FIG6( c ) is a simulation effect diagram of the difference in torque-to-current ratio obtained by using the control method of the present invention and the traditional vector control method when the motor speed is 1500 r / min.

[0055] FIG. 7( a ) is a diagram showing the d-axis current simulation effect obtained by using the control method of the present invention when the motor speed is 2500 r / min.

[0056] FIG. 7( b ) is a diagram showing the d-axis current simulation effect obtained by using a traditional vector control method when the motor speed is 2500 r / min in the present invention.

[0057] FIG7( c ) is a simulation effect diagram of the difference in d-axis current obtained by using the control method of the present invention and the traditional vector control method when the motor speed is 2500 r / min.

[0058] FIG8( a ) is a diagram showing the simulation effect of the q-axis current obtained by using the control method of the present invention when the motor speed is 2500 r / min.

[0059] FIG8( b ) is a diagram showing the simulation effect of the q-axis current obtained by using a traditional vector control method when the motor speed is 2500 r / min in the present invention.

[0060] FIG8( c ) is a simulation effect diagram of the difference in q-axis current obtained by using the control method of the present invention and the traditional vector control method when the motor speed is 2500 r / min.

[0061] FIG9( a ) is a diagram showing a simulation effect of the torque-to-current ratio obtained by using the control method of the present invention when the motor speed is 2500 r / min.

[0062] FIG9( b ) is a diagram showing the simulation effect of the torque-to-current ratio obtained by using the traditional vector control method when the motor speed is 2500 r / min in the present invention.

[0063] FIG9( c ) is a simulation effect diagram of the difference in torque-to-current ratio obtained by using the control method of the present invention and the traditional vector control method when the motor speed is 2500 r / min. DETAILED DESCRIPTION

[0064] In combination with the present invention Figure 1-3According to the content of the present invention, a specific embodiment of the maximum torque-to-current ratio control method of a surface-mounted permanent magnet motor based on a vector magnetic circuit is completed, and Figures 4 (a)-9 (c) are simulation results of the specific implementation.

[0065] The electromagnetic torque equation based on the vector magnetic circuit and the maximum torque current ratio control method of the surface mounted permanent magnet motor proposed in the present invention include the following steps:

[0066] Step 1: Build the SMD PM motor Axis and Axis vector magnetic circuit model, the equivalent magnetic reactance With magnetic resistance The inverse tangent of the ratio is regarded as the iron loss angle , using the iron loss angle to induce the influence of eddy current and hysteresis effect of iron loss on electromagnetic torque;

[0067] In the surface mounted permanent magnet motor Axis and Two vector magnetic circuit parameters, magnetic induction L and magnetic capacitance C, are introduced into the axis magnetic circuit model to construct Axis and The axial vector magnetic circuit model uses magnetic induction L and magnetic capacitance C to characterize the magnitude of eddy current and hysteresis effects that cause iron loss; both magnetic induction L and magnetic capacitance C make the magnetic flux lag behind the magnetomotive force or current, so the equivalent magnetic induction parameters can be used The combined effect of equivalent magnetic induction L and magnetic capacitance C; Axis and In the axial vector magnetic circuit model, the angle at which the magnetic flux lags behind the magnetomotive force or current is the iron loss angle. , which can be expressed as:

[0068] (1)

[0069] make

[0070] (2)

[0071] say is the equivalent magnetic induction parameter, which can be measured by experiment. In the present invention, the change of equivalent magnetic induction coefficient is not considered, and the equivalent magnetic induction coefficient is considered to be a fixed parameter. Since the magnetic resistance is expressed as , the iron loss angle of the surface mounted permanent magnet motor is expressed as:

[0072] (3)

[0073] In formula (1) to formula (3), L is The magnetic induction in the coordinate system, C is Magnetic capacitance in the coordinate system, L eq for The equivalent magnetic induction in the coordinate system is, for The magnetic resistance in the coordinate system, for The inductance in the coordinate system, is the equivalent magnetic induction coefficient, is the iron loss angle, is the rotor electrical angular velocity, is the number of turns of the armature winding.

[0074] Step 2: On the surface mount permanent magnet motor Axis and Introducing equivalent magnetic induction parameters into the axis magnetic circuit equation , and then perform coordinate transformation to obtain In the coordinate system Axis and Axis magnetic circuit equation:

[0075] (4)

[0076] In formula (4), and for Coordinate system Axial magnetomotive force and Axial magnetomotive force, and for Coordinate system Axis flux and Axis flux, and for Coordinate system Shaft current and Shaft current, for The magnetic resistance in the coordinate system, for The equivalent magnetic induction in the coordinate system is, for The inductance in the coordinate system, is the permanent magnet flux, is the electrical angular velocity of the rotor, is the differential operator.

[0077] When the motor is running stably, Axis and The magnetic circuit of the shaft is in a stable state, and further we can get:

[0078] (5)

[0079] Combining equations (3) and (5), we can get The flux equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit in the coordinate system is:

[0080] [ 1 − tan d tan d 1 ] [ ψ d ψ q ] = [ L s 0 0 L s ] [ i d i q ] + [ ψ f 0 ] (6)

[0081] Furthermore, multiply both sides of equation (6) by , we can get:

[0082] M d [ ψ d ψ q ] = [ L s cos d 0 0 L s cos d ] [ i d i q ] + [ ψ f cos d 0 ] (7)

[0083] In formula (7), M d = [ cos d − sin d sin d cos d ] is the coordinate transformation matrix, which is The coordinate system rotates in the direction of lag by the iron loss angle The matrix of , we get the RL coordinate system, such as Figure 1 shown.

[0084] In formula (5-7), and for In the coordinate system Axis flux and Axis flux, and for In the coordinate system Shaft current and Shaft current, for The inductance in the coordinate system, is the permanent magnet flux, is the electrical angular velocity of the rotor.

[0085] Axis and The shaft voltage (flux) is transformed by the coordinate matrix After transformation, we get Axis and Shaft voltage (flux), further according to formula (7), the flux equation of the surface mounted permanent magnet motor based on the vector magnetic circuit and RL coordinate system can be obtained:

[0086] [ ψ R ψ L ] = [ L s cos d 0 0 L s cos d ] [ i d i q ] + [ ψ f cos d 0 ] (8)

[0087] The voltage equation of the surface-mounted permanent magnet motor in the RL coordinate system:

[0088] [ u R u L ] = [ R s 0 0 R s ] [ i R i L ] + [ p ψ R p ψ L ] + [ − oops L oops R ] (9)

[0089] Further, according to the relationship [ i R i L ] = M d [ i d i q ] And formula (8), use Axis and Shaft current replacement Axis and The shaft current Axis and Substituting the axial flux into equation (9), we get:

[0090] [ u R u L ] = [ R s cos d + pL s cos d − ( R s sin d + oh L s cos d ) R s sin d + oh L s cos d R s cos d + pL s cos d ] [ i d i q ] + [ 0 oops f cos d ] (10)

[0091] because , ignoring the According to formula (10), the voltage equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit and RL coordinate system is obtained:

[0092] [ u R u L ] = [ R s cos d + pL s cos d − oh L s cos d oh L s cos d R s cos d + pL s cos d ] [ i d i q ] + [ 0 oops f cos d ] (11)

[0093] Multiply both sides of equation (8) by the inverse matrix of the RL coordinate transformation matrix ,get The flux equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit in the coordinate system is:

[0094] [ ψ d ψ q ] = [ L s cos 2 d L s sin d cos d − L s sin d cos d L s cos 2 d ] [ i d i q ] + [ ψ f cos 2 d − ψ f sin d cos d ] (12)

[0095] Formula (8-12), and for Magnetic flux in the coordinate system, and is the RL coordinate system Axis flux and Axis flux, and is the RL coordinate system Shaft voltage and Shaft voltage, and is the RL coordinate system Shaft current and Shaft current, and for The current in the coordinate system, for The inductance in the coordinate system, for The resistance in the coordinate system, is the permanent magnet flux, is the iron loss angle, is the electrical angular velocity of the rotor, is the differential operator.

[0096] Step 3: Build The electromagnetic torque equation and motion equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit in the coordinate system:

[0097] The electromagnetic torque equation of the surface-mounted permanent magnet motor without considering the eddy current and hysteresis effects in the coordinate system is:

[0098] (13)

[0099] Based on the vector magnetic circuit Axis and Substituting the axial flux (12) into (13), we get The electromagnetic torque equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit considering the eddy current and hysteresis effects in the coordinate system is:

[0100] T d = 3 2 p n [ 1 2 L s sin 2 d *( i d 2 + i q 2 ) + ψ f cos 2 d * i q + 1 2 ψ f sin 2 d * i d ] (14)

[0101] The electromagnetic torque equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit proposed in the present invention includes Axis and Axis current component, so the maximum torque current ratio control method is used. It is necessary to find the optimal combination of cross-axis and direct-axis current under the current operating state. The expression is as follows:

[0102] { T d = 3 2 p n [ 1 2 L s sin 2 d *( i d 2 + i q 2 ) + ψ f cos 2 d * i q + 1 2 ψ f sin 2 d * i d ] i s = minutes i d 2 + i q 2 (15)

[0103] like Figure 2 As shown, the relationship between the stator current vector and the quadrature and direct axis currents can be expressed as:

[0104] (16)

[0105] Substituting equation (16) into equation (15), we get the relationship between electromagnetic torque and stator current vector angle:

[0106] T d = 3 2 p n [ 1 2 L s i s 2 sin 2 d + ψ f cos 2 d ( i s sin β ) + 1 2 ψ f sin 2 d ( i s cos β )] (17)

[0107] The stator current vector in equation (17) is After phase shifting, the expression of electromagnetic torque per unit current is obtained:

[0108] (18)

[0109] When the derivative of the unit current electromagnetic torque with respect to the stator current vector angle is equal to zero, the unit current electromagnetic torque reaches a maximum value. At this time, the motor operating point corresponding to the stator current vector angle is the MTPA (MaxiumuTorqueper Ampere) control point, which is specifically expressed as:

[0110] (19)

[0111] Further, we obtain:

[0112] (20)

[0113] Furthermore, the motion equation of the surface-mounted permanent magnet motor is obtained:

[0114] (twenty one)

[0115] In formula (13-21), and for Magnetic flux in the coordinate system, for The inductance in the coordinate system, and for The current in the coordinate system, for The stator current vector in the coordinate system is: for and The angle of the axis, is the permanent magnet flux, is the number of motor pole pairs, is the iron loss angle, is the electrical angular velocity of the rotor, is the moment of inertia, for The electromagnetic torque of the surface-mounted permanent magnet motor without considering the eddy current and hysteresis effects in the coordinate system, for The electromagnetic torque of the surface-mounted permanent magnet motor based on the vector magnetic circuit considering the eddy current and hysteresis effects in the coordinate system, is the load torque, is the damping coefficient of the motor.

[0116] Step 4: Establish the maximum torque-to-current ratio control method of the surface-mounted permanent magnet motor based on the vector magnetic circuit:

[0117] like Figure 3 As shown, the three-phase current of the surface-mounted permanent magnet motor is sampled to obtain the sampled value , , ,Will , , After coordinate transformation, we get Current sampling value in the coordinate system and ;

[0118] Rotor electrical angular velocity The rotor electrical angular velocity setting The error is obtained by PI controller to obtain the stator current vector , obtained through the relationship between the stator current vector and the quadrature and direct axis currents Axis and Shaft current setting value and , specifically:

[0119]

[0120]

[0121] Will and With the set value and The error is input into two PI controllers respectively to obtain the voltage setting value in the RL coordinate system and ,Will and Through the coordinate transformation matrix The inverse transformation yields Voltage setting value in coordinate system and , through the inverse Park transform, and then Voltage setting value in coordinate system and Transformation Voltage setting value in coordinate system and ,use and The synthesized voltage space vector is input into the voltage space vector modulation module SVPWM for modulation, and the state coding values ​​of the three half bridges at that moment are output to control the MOS tube switches of the three-phase inverter to control the motor.

[0122] Perform vector control simulation on the surface-mount permanent magnet motor. First, adjust the motor speed to 1500r / min and the load to 5N·m. Then adjust the motor speed to 2500r / min and the load to 5N·m. Observe the motor speed. Axis and The change of shaft current and the ratio of torque to current are compared with the motor model and control method used in the present invention and the traditional motor model. The effect of the control method is compared; the influence of iron loss on the motor control performance at different speeds is compared to verify the feasibility of the electromagnetic torque equation based on the vector magnetic circuit and the maximum torque current ratio of the surface-mounted permanent magnet motor proposed in the present invention. The parameters of the surface-mounted permanent magnet motor in the simulation are shown in Table 1:

[0123] Table 1 Parameters of surface mounted permanent magnet motor in simulation

[0124]

[0125] As shown in Figures 4(a)-5(c) and 7(a)-8(c), the control method proposed by the present invention Axis and The current of the axis is higher than that of the traditional vector control Axis and From the shaft current, it can be seen that in the actual motor working condition, the eddy current and hysteresis effect have an obstructive effect on the current, indicating the correctness of the motor model established in the present invention and the proposed electromagnetic torque equation.

[0126] As shown in Figures 6(a)-6(c) and Figures 9(a)-9(c), the torque-to-current ratio of the motor at a speed of 2500 r / min is smaller than that at 1500 r / min. This shows that when the load torque is the same, the higher the speed, the greater the eddy current and hysteresis effects will hinder the current, and the greater the impact on the motor performance. This is indeed of great significance for the precise control of the output torque under actual operating conditions.

Claims

1. The electromagnetic torque equation of the motor based on the vector magnetic circuit is characterized by: The electromagnetic torque equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit considering the eddy current and hysteresis effects in the coordinate system is expressed as follows: （1） in, and for In the coordinate system Shaft current and Shaft current, for The inductance in the coordinate system, is the permanent magnet flux, is the number of motor pole pairs, is the iron loss angle, for Electromagnetic torque of surface-mounted permanent magnet motor based on vector magnetic circuit considering eddy current and hysteresis effects in coordinate system.

2. A method for calculating the maximum torque current ratio of a motor based on a vector magnetic circuit, characterized in that: Based on the motor electromagnetic torque equation based on the vector magnetic circuit as claimed in claim 1, the maximum torque current ratio is calculated as follows: （2） The relationship between the stator current vector and the quadrature and direct axis currents is expressed as: （3） in, and for In the coordinate system Shaft current and Shaft current, for The stator current vector in the coordinate system is: is the stator current vector angle, is the stator current vector and The angle of the axis, is the permanent magnet flux, is the number of motor pole pairs, is the iron loss angle.

3. The method for calculating the maximum torque current ratio of a motor based on a vector magnetic circuit according to claim 2, characterized in that: Substituting equation (3) into the electromagnetic torque equation in equation (2), we get the electromagnetic torque The stator current vector angle The relationship is: （5） Stator current vector Perform phase shift processing to further obtain the unit current electromagnetic torque The expression is: （6） Electromagnetic torque per unit current The maximum relationship needs to be satisfied: （7） Further, we obtain: （8）。 4. The method for calculating the maximum torque current ratio of a motor based on a vector magnetic circuit according to claim 1 or 2, characterized in that: In the surface mounted permanent magnet motor Axis and Two vector magnetic circuit parameters, magnetic induction L and magnetic capacitance C, are introduced into the axial vector magnetic circuit model. Both magnetic induction L and magnetic capacitance C make the magnetic flux lag behind the magnetomotive force or current. The angle at which the magnetic flux lags behind the magnetomotive force or current is the iron loss angle. , expressed as: （1） make （2） say is the equivalent magnetic induction parameter; Since the magnetic resistance is expressed as , iron loss angle of surface mounted permanent magnet motor It is expressed as: （3） L is The magnetic induction in the coordinate system, C is Magnetic capacitance in the coordinate system, L eq for The equivalent magnetic induction in the coordinate system is, for The magnetic resistance in the coordinate system, for The inductance in the coordinate system, is the equivalent magnetic induction coefficient, is the iron loss angle, is the rotor electrical angular velocity, is the number of turns of the armature winding.

5. The method for calculating the maximum torque current ratio of a motor based on a vector magnetic circuit according to claim 2, characterized in that: The voltage equation of the surface mounted permanent magnet motor based on the vector magnetic circuit is: （9） in, and is the voltage in the RL coordinate system, and for The current in the coordinate system, for The inductance in the coordinate system, for The resistance in the coordinate system, is the permanent magnet flux, is the iron loss angle, is the electrical angular velocity of the rotor, is the differential operator.

6. The method for calculating the maximum torque current ratio of a motor based on a vector magnetic circuit according to claim 5, characterized in that: The voltage in the RL coordinate system is The voltage relationship in the coordinate system is as follows: （10） in, is the coordinate transformation matrix, expressed as: （11）。 7. A motor control method based on a vector magnetic circuit, characterized in that: The steps include: Sampling the three-phase current of the surface-mounted permanent magnet motor to obtain the sampled value , , ,Will , , After coordinate transformation, we get Current sampling value in the coordinate system and ; Rotor electrical angular velocity and the rotor electrical angular velocity setting value The error is obtained by PI controller to obtain the stator current vector , obtained through the relationship between the stator current vector and the quadrature and direct axis currents Axis and Shaft current setting value and , specifically: ； ； ； represents the stator current vector angle, represents the iron loss angle; Will Current sampling value in the coordinate system and With the set value and The error is input into two PI controllers respectively to obtain the voltage setting value in the RL coordinate system and ,Will and Through the coordinate transformation matrix The inverse transformation yields Voltage setting value in coordinate system and , through the inverse Park transform, and then Voltage setting value in coordinate system and Transformation Voltage setting value in coordinate system and ,use and The synthesized voltage space vector is input into the voltage space vector modulation module for modulation, and the state coding values ​​of the three half bridges are output to control the MOS tube switches of the three-phase inverter to control the motor.

8. The motor control method based on vector magnetic circuit according to claim 7, characterized in that: Stator current vector angle The corresponding motor operating point is the MTPA control point.

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