Calculation method of electromagnetic torque and maximum torque-to-current ratio of motor and motor control method based on vector magnetic circuit

Abstract

The present invention belongs to the technical field of motor control, and specifically discloses a motor electromagnetic torque, maximum torque current ratio calculation method and motor control method based on a vector magnetic circuit. First, a vector magnetic circuit model of a permanent magnet motor is established, and the influence of eddy current and hysteresis effects in magnetic materials on the electromagnetic torque of the motor is characterized by equivalent magnetic induction. The permanent magnet motor vector magnetic circuit electromagnetic torque equation containing equivalent magnetic induction is established through coordinate transformation, and then a permanent magnet motor maximum torque current ratio control method is further proposed. The method proposed in the present invention fully considers the influence of eddy current and hysteresis effects in magnetic materials on the electromagnetic torque of the motor, and the proposed maximum torque current ratio control makes the torque control of the permanent magnet motor more accurate.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor control, and in particular relates to a method for calculating the electromagnetic torque and maximum torque-to-current ratio of a motor based on a vector magnetic circuit, and a motor 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 a method for calculating the electromagnetic torque 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 a method for calculating the electromagnetic torque of 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 a vector magnetic circuit in a dq coordinate system considering eddy current and hysteresis effects is expressed as follows:

[0006]

[0007] Among them, i d and i q are the d-axis current and q-axis current in the dq coordinate system, L s is the inductance in the dq coordinate system, ψ f is the permanent magnet flux, p n is the number of motor pole pairs, δ is the iron loss angle, T δ It is the electromagnetic torque of the surface-mounted permanent magnet motor based on vector magnetic circuit considering eddy current and hysteresis effects in dq coordinate system.

[0008] 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, wherein the electromagnetic torque equation of the surface-mounted permanent magnet motor includes the d-axis current component i d and the q-axis current component i q 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:

[0009]

[0010] The relationship between the stator current vector and the quadrature and direct axis currents is expressed as:

[0011]

[0012] Among them, i d and i q is the d-axis current and q-axis current in the dq coordinate system, i s is the stator current vector in the dq coordinate system, β is the stator current vector angle, and is the stator current vector i s The angle with the d-axis, ψ f is the permanent magnet flux, p n is the number of motor pole pairs, and δ is the iron loss angle.

[0013] Furthermore, by substituting equation (3) into the electromagnetic torque equation of equation (2), we can obtain the electromagnetic torque T δ The relationship with the stator current vector angle β is:

[0014]

[0015] Stator current vector i s After phase shifting, the expression of unit current electromagnetic torque F(β) is obtained as follows:

[0016]

[0017] 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. Specifically, the relationship that needs to be satisfied when the unit current electromagnetic torque F(β) is maximum is:

[0018]

[0019] Further, we obtain:

[0020]

[0021] Furthermore, the magnetic induction is introduced into the d-axis and q-axis vector magnetic circuit models of the surface-mounted permanent magnet motor. and magnetic capacitance C, two vector magnetic circuit parameters, magnetic induction Both the magnetic flux and the magnetic capacitance C cause the magnetic flux to 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 δ, which is expressed as:

[0022]

[0023] make

[0024]

[0025] k is called the equivalent magnetic induction parameter;

[0026] Since the magnetic resistance is expressed as The iron loss angle δ of the surface mounted permanent magnet motor is expressed as:

[0027] δ=arctan(ωL s k) (3)

[0028] is the magnetic induction in the dq coordinate system, C is the magnetic capacitance in the dq coordinate system, is the equivalent magnetic induction in the dq coordinate system, is the magnetic resistance in the dq coordinate system, L s is the inductance in the dq coordinate system, k is the equivalent magnetic induction coefficient, δ is the iron loss angle, ω is the rotor electrical angular velocity, and N is the number of turns of the armature winding.

[0029] Furthermore, the voltage equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit is:

[0030]

[0031] in, and for The voltage in the coordinate system, i d and i q is the current in the dq coordinate system, L sis the inductance in the dq coordinate system, R s is the resistance in the dq coordinate system, ψ f is the permanent magnet flux, δ is the iron loss angle, ω is the electrical angular velocity of the rotor, and p is the differential operator.

[0032] The relationship between the voltage in the coordinate system and the voltage in the dq coordinate system is as follows:

[0033]

[0034] Among them, M δ is the coordinate transformation matrix, expressed as:

[0035]

[0036] The present invention also proposes a surface mounted permanent magnet motor control method based on a vector magnetic circuit, comprising the following steps:

[0037] The three-phase current of the surface-mounted permanent magnet motor is sampled to obtain the sampling value i a * 、i b * 、i c * , change i a * 、i b * 、i c * After coordinate transformation, the current sampling value i in the dq coordinate system is obtained d * and i q * ;

[0038] Rotor electrical angular velocity ω * The error with the rotor electrical angular velocity set value ω is obtained by the PI controller to obtain the stator current vector i s , the d-axis and q-axis current setting values ​​i are obtained through the relationship between the stator current vector and the quadrature and direct axis currents d and i q , specifically:

[0039] i q =i s sinβ

[0040] i d =i s cosβ

[0041]

[0042] β represents the stator current vector angle, δ represents the iron loss angle;

[0043] The current sampling value i in the dq coordinate system d * and i q * With the set value i d and i q The error is input into two PI controllers respectively, and we get Voltage setting value in coordinate system and Will and Through the coordinate transformation matrix M δ The inverse transformation obtains the voltage setting value u in the dq coordinate system d and u q , through the inverse Park transformation, the voltage setting value u in the dq coordinate system is d and u q Transform to obtain the voltage setting value u in the α-β coordinate system α and u β , use u α and u β 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.

[0044] Furthermore, the motor operating point corresponding to the stator current vector angle β in the present invention is the MTPA control point.

[0045] 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:

[0046] (1) The maximum torque current ratio control method proposed by the present invention based on the electromagnetic torque equation of the vector magnetic circuit maximizes the torque output by the permanent magnet motor under this control method. d =0 control method, the torque utilization rate is higher, and the torque control of the permanent magnet motor is more precise;

[0047] (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

[0048] In order to more clearly and intuitively understand the relevant principles of the present invention, the following figures are attached for easy understanding.

[0049] Figure 1 It is a schematic diagram of the relationship between the RL coordinate system and the dq coordinate system established in the present invention;

[0050] Figure 2 is the d-axis current i in the maximum torque current ratio d , q-axis current i q With the stator current vector i s Schematic diagram of the relationship between

[0051] 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;

[0052] 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;

[0053] FIG4( b ) is a diagram showing the d-axis current simulation effect obtained by using a conventional vector control method when the motor speed is 1500 r / min in the present invention;

[0054] FIG4(c) is a simulation effect diagram of the difference in d-axis current obtained by the control method of the present invention and the traditional vector control method when the motor speed is 1500 r / min;

[0055] 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;

[0056] FIG5( b ) is a diagram showing the simulation effect of the q-axis current obtained by using a conventional vector control method when the motor speed is 1500 r / min in the present invention;

[0057] FIG5(c) is a simulation effect diagram of the difference between the q-axis current obtained by the control method of the present invention and the traditional vector control method when the motor speed is 1500 r / min in the present invention; FIG6(a) is a simulation effect diagram of the torque-current ratio obtained by the control method of the present invention when the motor speed is 1500 r / min in the present invention;

[0058] FIG6( b ) is a simulation effect diagram of the torque-to-current ratio obtained by using a conventional vector control method when the motor speed is 1500 r / min in the present invention;

[0059] FIG6( c ) is a simulation effect diagram of the difference in torque-to-current ratio obtained by the control method of the present invention and the traditional vector control method when the motor speed is 1500 r / min;

[0060] 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;

[0061] FIG7( b ) is a diagram showing the d-axis current simulation effect obtained by using a conventional vector control method when the motor speed is 2500 r / min in the present invention;

[0062] FIG. 7( c ) is a simulation effect diagram of the difference in d-axis current obtained by the control method of the present invention and the traditional vector control method when the motor speed is 2500 r / min;

[0063] 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;

[0064] FIG8( b ) is a diagram showing the simulation effect of the q-axis current obtained by using the conventional vector control method when the motor speed is 2500 r / min in the present invention;

[0065] FIG8(c) is a simulation effect diagram of the difference between the q-axis current obtained by the control method of the present invention and the traditional vector control method when the motor speed is 2500 r / min in the present invention; FIG9(a) is a simulation effect diagram of the torque-current ratio obtained by the control method of the present invention when the motor speed is 2500 r / min in the present invention;

[0066] FIG9( b ) is a simulation effect diagram of the torque-to-current ratio obtained by using a conventional vector control method when the motor speed is 2500 r / min in the present invention;

[0067] 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

[0068] In combination with the present invention Figure 1-3 The invention has completed a specific embodiment of a method for controlling the maximum torque current ratio of a surface-mounted permanent magnet motor based on a vector magnetic circuit, and the attached Figures 4(a)-9(c) The simulation results are for specific implementation.

[0069] 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:

[0070] Step 1: Establish the d-axis and q-axis vector magnetic circuit models of the surface-mounted permanent magnet motor and convert the equivalent magnetic reactance With magnetic resistance The arc tangent value of the ratio is regarded as the iron loss angle δ, which is used to induce the influence of the eddy current and hysteresis effect of iron loss on the electromagnetic torque;

[0071] Introducing magnetic induction into the d-axis and q-axis magnetic circuit models of surface-mounted permanent magnet motors The two vector magnetic circuit parameters of magnetic induction and magnetic capacitance C are used to construct the d-axis and q-axis vector magnetic circuit models. The magnetic induction C and magnetic capacitance C characterize the magnitude of the eddy current and hysteresis effect that cause iron loss; Both the magnetic flux and the magnetic capacitance C lag behind the magnetomotive force or current, so the equivalent magnetic induction parameter can be used Equivalent magnetic induction and the magnetic capacitance C; in the d-axis and q-axis vector magnetic circuit models, the angle at which the magnetic flux lags behind the magnetomotive force or current is the iron loss angle δ, which can be expressed as:

[0072]

[0073] make

[0074]

[0075] k is called the equivalent magnetic induction parameter, which can be measured experimentally. In the present invention, the change of the 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:

[0076] δ=arctan(ωL s k) (3)

[0077] In formula (1) to formula (3), is the magnetic induction in the dq coordinate system, C is the magnetic capacitance in the dq coordinate system, is the equivalent magnetic induction in the dq coordinate system, is the magnetic resistance in the dq coordinate system, L s is the inductance in the dq coordinate system, k is the equivalent magnetic induction coefficient, δ is the iron loss angle, ω is the rotor electrical angular velocity, and N is the number of turns of the armature winding.

[0078] Step 2: Introduce equivalent magnetic induction parameters into the d-axis and q-axis magnetic circuit equations of the surface-mounted permanent magnet motor Then perform coordinate transformation to obtain the d-axis and q-axis magnetic circuit equations in the dq coordinate system:

[0079]

[0080] In formula (4), and is the d-axis magnetomotive force and q-axis magnetomotive force in the dq coordinate system, Φ d and Φ q is the d-axis magnetic flux and q-axis magnetic flux in the dq coordinate system, i d and i q are the d-axis current and q-axis current in the dq coordinate system, is the magnetic resistance in the dq coordinate system, is the equivalent magnetic induction in the dq coordinate system, L s is the inductance in the dq coordinate system, ψ f is the permanent magnet flux, ω is the electrical angular velocity of the rotor, and p is the differential operator.

[0081] When the motor is running stably, it is considered that the magnetic circuits of the d-axis and q-axis are in a stable state, and further, it can be obtained that:

[0082]

[0083] Combining equations (3) and (5), we can obtain the flux equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit in the dq coordinate system:

[0084]

[0085] Furthermore, multiplying both sides of equation (6) by cosδ, we can obtain:

[0086]

[0087] In formula (7), is the coordinate transformation matrix, which rotates the dq coordinate system in the direction of lag by the iron loss angle δ, and obtains Coordinate system, such as Figure 1 shown.

[0088] In formula (5-7), ψ d and ψ q is the d-axis magnetic flux and q-axis magnetic flux in the dq coordinate system, i d and i q are the d-axis current and q-axis current in the dq coordinate system, L s is the inductance in the dq coordinate system, ψ f is the permanent magnet flux, and ω is the electrical angular velocity of the rotor.

[0089] The d-axis and q-axis voltages (flux) are transformed by the coordinate transformation matrix M δ After transformation, we get Axis and Shaft voltage (flux), further according to formula (7) we can get the vector magnetic circuit and The flux equation of the surface mounted permanent magnet motor in the coordinate system is:

[0090]

[0091] The voltage equation of the surface mounted permanent magnet motor in the coordinate system:

[0092]

[0093] Further, according to the relationship and equation (8), using the d-axis and q-axis currents to replace Axis and The shaft current Axis and Substituting the axial flux into equation (9), we get:

[0094]

[0095] Due to R s sinδ<<ωL s cosδ, ignoring R in equation (10) s sinδ, according to formula (10), based on the vector magnetic circuit and The voltage equation of the surface mounted permanent magnet motor in the coordinate system is:

[0096]

[0097] Multiply both sides of equation (8) by The inverse matrix M of the coordinate transformation matrix δ -1 , the flux equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit in the dq coordinate system is obtained:

[0098]

[0099] Formula (8-12), ψ d and ψ q is the magnetic flux in the dq coordinate system, and for In the coordinate system Axis flux and Axis flux, and for In the coordinate system Shaft voltage and Shaft voltage, and for In the coordinate system Shaft current and Shaft current, i d and i q is the current in the dq coordinate system, L s is the inductance in the dq coordinate system, R s is the resistance in the dq coordinate system, ψ f is the permanent magnet flux, δ is the iron loss angle, ω is the electrical angular velocity of the rotor, and p is the differential operator.

[0100] Step 3: Establish the electromagnetic torque equation and motion equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit in the dq coordinate system:

[0101] The electromagnetic torque equation of the surface-mounted permanent magnet motor without considering eddy current and hysteresis effects in the dq coordinate system is:

[0102]

[0103] Substituting the d-axis and q-axis flux based on the vector magnetic circuit, that is, equation (12), into equation (13), 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 dq coordinate system is obtained:

[0104]

[0105] The electromagnetic torque equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit proposed in the present invention contains d-axis and q-axis current components. Therefore, the control method of the maximum torque current ratio is adopted. It is necessary to find the optimal quadrature and direct axis current combination under the current operating state. The expression is as follows:

[0106]

[0107] like Figure 2 As shown, the relationship between the stator current vector and the quadrature and direct axis currents can be expressed as:

[0108]

[0109] Substituting equation (16) into equation (15), we get the relationship between electromagnetic torque and stator current vector angle:

[0110]

[0111] The stator current vector i in equation (17) is s After phase shifting, the expression of electromagnetic torque per unit current is obtained:

[0112]

[0113] 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:

[0114]

[0115] Further, we obtain:

[0116]

[0117] Furthermore, the motion equation of the surface-mounted permanent magnet motor is obtained:

[0118]

[0119] In formula (13-21), ψ d and ψ qis the magnetic flux in the dq coordinate system, L s is the inductance in the dq coordinate system, i d and i q is the current in the dq coordinate system, i s is the stator current vector in the dq coordinate system, β is i s The angle with the d-axis, ψ f is the permanent magnet flux, p n is the number of motor pole pairs, δ is the iron loss angle, ω is the electrical angular velocity of the rotor, J is the moment of inertia, T e is the electromagnetic torque of the surface-mounted permanent magnet motor in the dq coordinate system without considering the eddy current and hysteresis effects, T δ is the electromagnetic torque of the surface-mounted permanent magnet motor based on vector magnetic circuit considering eddy current and hysteresis effects in dq coordinate system, T L is the load torque, and B is the damping coefficient of the motor.

[0120] Step 4: Establish the maximum torque-to-current ratio control method of the surface-mounted permanent magnet motor based on the vector magnetic circuit:

[0121] like Figure 3 As shown, the three-phase current of the surface-mounted permanent magnet motor is sampled to obtain the sampling value i a * 、i b * 、i c * , change i a * 、i b * 、i c * After coordinate transformation, the current sampling value i in the dq coordinate system is obtained d * and i q * ;

[0122] Rotor electrical angular velocity ω and rotor electrical angular velocity setting value ω * The error is obtained by PI controller to obtain the stator current vector i s , the d-axis and q-axis current setting values ​​i are obtained through the relationship between the stator current vector and the quadrature and direct axis currents d and i q , specifically:

[0123] i q =f 1 (i s )=i s sinβ

[0124] i d =f 2 (is )=i s cosβ

[0125] will i d * and i q * With the set value i d and i q The error is input into two PI controllers respectively, and we get Voltage setting value in coordinate system and will u R and u L Through the coordinate transformation matrix M δ The inverse transformation obtains the voltage setting value u in the dq coordinate system d and u q , through the inverse Park transformation, the voltage setting value u in the dq coordinate system is d and u q Transform to obtain the voltage setting value u in the α-β coordinate system α and u β , use u α and u β 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.

[0126] The vector control simulation of the surface mounted permanent magnet motor is carried out. The motor speed is first adjusted to 1500r / min and the load is 5N·m. Then the motor speed is adjusted to 2500r / min and the load is still 5N·m. The changes of the motor d-axis and q-axis currents and the ratio of torque to current are observed. The motor model and control method used in the present invention are compared with the traditional motor model i d =0 control method; respectively compare the influence of iron loss on the motor control performance at different speeds, 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:

[0127] Table 1 Parameters of surface mounted permanent magnet motor in simulation

[0128]

[0129] like Figure 4(a)-5(c) and Figures 7(a)-8(c)As shown, the currents of the d-axis and q-axis in the control method proposed in the present invention are higher than those in the traditional vector control. It can be seen that in actual motor working conditions, eddy current and hysteresis effects 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.

[0130] like Figure 6(a)-6(c) and Figure 9(a)-9(c) As shown in the figure, the torque-to-current ratio of the motor at a speed of 2500r / min is smaller than that at 1500r / min. It can be seen 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. A method for calculating the electromagnetic torque of a motor based on a vector magnetic circuit, characterized in that: Introducing magnetic induction into the d-axis and q-axis vector magnetic circuit models of surface-mounted permanent magnet motors and magnetic capacitance C are two vector magnetic circuit parameters, magnetic induction and magnetic capacitance C both make the magnetic flux lag behind the magnetomotive force or current. The angle of magnetic flux lags behind the magnetomotive force or current is the iron loss angle δ. 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 dq coordinate system is expressed as follows: Among them, i d and i q are the d-axis current and q-axis current in the dq coordinate system, L s is the inductance in the dq coordinate system, ψ f is the permanent magnet flux, p n is the number of motor pole pairs, δ is the iron loss angle, T δ It is the electromagnetic torque of the surface-mounted permanent magnet motor based on vector magnetic circuit considering eddy current and hysteresis effects in dq 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 calculation method based on the vector magnetic circuit as claimed in claim 1, the maximum torque current ratio is calculated as follows: The relationship between the stator current vector and the quadrature and direct axis currents is expressed as: Among them, i d and i q is the d-axis current and q-axis current in the dq coordinate system, i s is the stator current vector in the dq coordinate system, β is the stator current vector angle, and is the stator current vector i s The angle with the d-axis, ψ f is the permanent magnet flux, p n is the number of motor pole pairs, and δ 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 T δ The relationship with the stator current vector angle β is: Stator current vector i s After phase shifting, the expression of unit current electromagnetic torque F(β) is further obtained as follows: When the unit current electromagnetic torque F(β) is maximum, the relationship needs to be satisfied: Further, we obtain:

4. 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 iron loss angle δ is expressed as: make k is called the equivalent magnetic induction parameter; Since the magnetic resistance is expressed as The iron loss angle δ of the surface mounted permanent magnet motor is expressed as: δ=arctan(ωL s k) (3) is the magnetic induction in the dq coordinate system, C is the magnetic capacitance in the dq coordinate system, is the equivalent magnetic induction in the dq coordinate system, is the magnetic resistance in the dq coordinate system, L s is the inductance in the dq coordinate system, k is the equivalent magnetic induction coefficient, δ is the iron loss angle, ω is the rotor electrical angular velocity, and N 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: Among them, u R and u L for The voltage in the coordinate system, i d and i q is the current in the dq coordinate system, L s is the inductance in the dq coordinate system, R s is the resistance in the dq coordinate system, ψ f is the permanent magnet flux, δ is the iron loss angle, ω is the electrical angular velocity of the rotor, and p 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 relationship between the voltage in the coordinate system and the voltage in the dq coordinate system is as follows: Among them, M δ is the coordinate transformation matrix, expressed as:

7. A motor control method based on a vector magnetic circuit, characterized in that: Introducing magnetic induction into the d-axis and q-axis vector magnetic circuit models of surface-mounted permanent magnet motors and magnetic capacitance C are two vector magnetic circuit parameters, magnetic induction and magnetic capacitance C both 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 δ. The motor control method comprises the following steps: The three-phase current of the surface-mounted permanent magnet motor is sampled to obtain the sampling value i a * 、i b * 、i c * , change i a * 、i b * 、i c * After coordinate transformation, the current sampling value i in the dq coordinate system is obtained d * and i q * ; Rotor electrical angular velocity ω * The error with the rotor electrical angular velocity set value ω is obtained by the PI controller to obtain the stator current vector i s , the d-axis and q-axis current setting values ​​i are obtained through the relationship between the stator current vector and the quadrature and direct axis currents d and i q , specifically: i q =i s sinβ i d =i s cosβ β represents the stator current vector angle, δ represents the iron loss angle; The current sampling value i in the dq coordinate system d * and i q * With the setting value i d and i q The error is input into two PI controllers respectively, and we get Voltage setting value in coordinate system and Said The coordinate system is obtained by rotating the dq coordinate system in the direction of lag by the iron loss angle δ. is the coordinate transformation matrix; will u R and u L Through the coordinate transformation matrix M δ The inverse transformation obtains the voltage setting value u in the dq coordinate system d and u q , through the inverse Park transformation, the voltage setting value u in the dq coordinate system is d and u q Transform to obtain the voltage setting value u in the α-β coordinate system α and u β , use u α and u β 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: The motor operating point corresponding to the stator current vector angle β is the MTPA control point.

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