Electromagnetic torque equation, maximum torque per ampere calculation method and control method for motor and based on vector magnetic circuit

Abstract

The present invention belongs to the technical field of motor control. Specifically disclosed are an electromagnetic torque equation, maximum torque per ampere calculation method and control method for a motor and based on a vector magnetic circuit. First, a vector magnetic circuit model for a permanent magnet motor is established; an equivalent magnetic inductance is used to characterize the influence of eddy current and hysteresis effects in a magnetic material on the electromagnetic torque of the motor; an electromagnetic torque equation for the permanent magnet motor and based on a vector magnetic circuit, which equation contains the equivalent magnetic inductance, is established by means of coordinate transformation; and then a maximum torque per ampere control method for the permanent magnet motor is further provided. The methods provided in the present invention take into full consideration the influence of eddy current and hysteresis effects in the magnetic material on the electromagnetic torque of the motor, and the provided maximum torque per ampere control makes the torque control of the permanent magnet motor more accurate.

Description

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

[0001] The application belongs to the technical field of motor control, and particularly relates to a motor electromagnetic torque equation, a maximum torque current ratio calculation method and a control method based on a vector magnetic circuit. BACKGROUND

[0002] A surface permanent magnet synchronous motor (SPMSM) has advantages of simple structure, high power density, wide speed regulation range and high working efficiency, and is widely applied to fields of industry, electric vehicles and household appliances. The performance of the SPMSM is not only affected by a motor structure, but also by a control algorithm, and vector control is one of the most common control methods for the SPMSM. The vector control of an alternating current motor is based on Clark transformation and Park transformation in coordinate transformation theory, and the three-phase stator current is decomposed into a torque component (quadrature axis current) and an excitation component (direct axis current) which are independent of each other, so that the magnetic field and torque of the alternating current motor are decoupled, and the alternating current motor has similar control performance to a direct current motor.

[0003] Professor Cheng Ming's team of Southeast University discovered a magnetic induction and magnetic capacity phenomenon in a magnetic circuit, established a vector magnetic circuit theory containing a magnetic resistance-magnetic induction-magnetic capacity three-element and a magnetic-electric power law, and provided a new method different from considering iron loss by using an equivalent resistance for considering the iron loss, wherein 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 capacity element corresponds to the magnetic hysteresis loss in the magnetic circuit. The magnetic induction and magnetic capacity are introduced into a permanent magnet motor model, the influence of the eddy current effect and the magnetic hysteresis effect on the stator magnetic flux excited by the permanent magnet magnetic flux and the armature current is considered, and a new permanent magnet motor control mathematical model is established based on the vector magnetic circuit theory. Since the model simultaneously considers the magnetic circuit and the electric circuit, the introduction of the iron loss is more reliable, but in the traditional control method, the magnetic motive force and the magnetic flux are in the same phase, and the influence of the eddy current and the magnetic hysteresis effect on the motor control performance is not considered. SUMMARY

[0004] The application aims to provide a motor electromagnetic torque equation based on a vector magnetic circuit, so that the permanent magnet motor modeling is more accurate, and the electromagnetic torque calculation is more accurate; the iron loss angle is used to represent the phase difference between the magnetic motive force and the magnetic flux caused by the iron loss, and the influence of the eddy current and the magnetic hysteresis effect in the magnetic material on the motor electromagnetic torque is fully considered.

[0005] The application proposes a surface-mounted permanent magnet motor electromagnetic torque equation based on a vector magnetic circuit, a surface-mounted permanent magnet motor electromagnetic torque equation based on a vector magnetic circuit considering eddy current and magnetic hysteresis effect in a d-q coordinate system, and is expressed as follows:

[0006] Wherein, i d and i q are d-axis current and q-axis current in a d-q coordinate system, L s is inductance in a d-q coordinate system, ψ f is permanent magnet flux linkage, p n is motor pole pair number, δ is iron loss angle, and T δ is surface-mounted permanent magnet motor electromagnetic torque based on a vector magnetic circuit considering eddy current and magnetic hysteresis effect in a-d-q coordinate system.

[0007] Based on the surface-mounted permanent magnet motor electromagnetic torque equation of the application, the application further proposes a surface-mounted permanent magnet motor maximum torque current ratio calculation method based on a vector magnetic circuit. The surface-mounted permanent magnet motor electromagnetic torque equation contains d-axis current component i d and q-axis current component i q , so the optimal cross-axis and direct-axis current combination under the current operating state needs to be found to obtain the maximum torque current ratio, and the expression is as follows:

[0008] The relationship between the stator current vector and the cross-axis and direct-axis current is expressed as:

[0009] Wherein, i d and i q are d-axis current and q-axis current in a d-q coordinate system, i s is a stator current vector in a d-q coordinate system, β is a stator current vector angle, which is an angle between the stator current vector i s and the d-axis, ψ f is permanent magnet flux linkage, p n is motor pole pair number, and δ is iron loss angle.

[0010] Further, the electromagnetic torque T δ and the stator current vector angle β are obtained by substituting formula (3) into the electromagnetic torque equation of formula (2), and the relationship is expressed as:

[0011] The stator current vector i s is subjected to phase shift processing, and the expression of the unit current electromagnetic torque F(β) is obtained as:

[0012] When the derivative of the unit current electromagnetic torque with respect to the stator current vector angle is zero, the unit current electromagnetic torque reaches its maximum value. At this point, the motor operating point corresponding to this stator current vector angle is the MTPA control point. Specifically, the relationship that the unit current electromagnetic torque F(β) needs to satisfy when it is at its maximum is as follows:

[0013] Furthermore, we obtain:

[0014] Furthermore, magnetic induction is introduced into the d-axis and q-axis vector magnetic circuit model of the surface-mount permanent magnet motor. Two vector magnetic circuit parameters, magnetocapacitance C and magnetic induction. Both magnetic flux and magnetocapacitance C cause magnetic flux to lag behind magnetomotive force or current. The angle by which magnetic flux lags behind magnetomotive force or current is called the iron loss angle δ, which is expressed as:

[0015] make

[0016] k is called the equivalent magnetic field parameter;

[0017] Since magnetic reluctance is expressed as The iron loss angle δ of a surface-mounted permanent magnet motor is expressed as: δ=arctan(ωL) s k) (3)

[0018] Let C be the magnetic induction in the dq coordinate system, and C be the magnetic capacitance in the dq coordinate system. The equivalent magnetic field in the dq coordinate system. Let L be the reluctance in the dq coordinate system. s Let be the inductance in the dq coordinate system, k be the equivalent magnetic flux density, δ be the iron loss angle, ω be the rotor electric angular velocity, and N be the number of turns in the armature winding.

[0019] Furthermore, the voltage equation for a surface-mount permanent magnet motor based on a vector magnetic circuit is as follows:

[0020] in, and for Voltage in coordinate system, i d and i q Let L be the current in the dq coordinate system. s Let R be the inductance in the dq coordinate system. s Let ψ be the resistance in the dq coordinate system. f δ is the permanent magnet flux linkage, ω is the iron loss angle, ω is the electric angular velocity of the rotor, and p is the differential operator.

[0021] The relationship between the voltage in the coordinate system and the voltage in the d-q coordinate system is as follows:

[0022] Wherein, M δ is a coordinate transformation matrix, and is expressed as:

[0023] The application further provides a surface-mounted permanent magnet motor control method based on a vector magnetic circuit, and the method comprises the following steps:

[0024] The three-phase currents of the surface-mounted permanent magnet motor are sampled to obtain sampling values i a * , i b * , i c * , i a * , i b * , i c * The sampling values i d * and i q * in the d-q coordinate system are obtained through coordinate transformation;

[0025] The error between the rotor electric angular velocity ω * and the rotor electric angular velocity set value ω is obtained through a PI controller to obtain a stator current vector i s The d-axis and q-axis current set values i d and i q are obtained through the relationship between the stator current vector and the cross-axis and direct-axis currents, and specifically, i q = i s sin β i d = i s cos β

[0026] β represents a stator current vector angle, and δ represents an iron loss angle;

[0027] The errors between the sampling values i d * and i q * in the d-q coordinate system and the set values i d and i q are respectively input into two PI controllers to obtain the voltage set values in the coordinate system and and are obtained through the coordinate transformation matrix M δ ​The inverse transformation obtains the voltage setting value u in the d-q coordinate system d and u q , through the inverse Park transformation, the voltage setting value u in the d-q coordinate system is transformed again d and u q , the voltage setting value u in the alpha-beta coordinate system is obtained α and u β , the voltage space vector is synthesized by u α and u β , the state code value of three half-bridges is output by inputting the voltage space vector modulation module for modulation, and the MOS tube switching control motor of the three-phase inverter is controlled.

[0028] Further, the motor operating point corresponding to the stator current vector angle β in the application is the MTPA control point.

[0029] Compared with the traditional electromagnetic torque equation and control method, the electromagnetic torque equation and control method of the application has the following beneficial effects:

[0030] (1) The maximum torque current ratio control method based on the electromagnetic torque equation of the vector magnetic circuit makes the output torque of the permanent magnet motor maximum under the control method, and the torque utilization rate is higher compared with the control method of i d = 0, and the torque control of the permanent magnet motor is more accurate;

[0031] (2) The electromagnetic torque equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit solves the problem that the calculated value and the actual measured value of the electromagnetic torque of the motor are inconsistent under the real operating condition, and has great significance for the design of the motor and the numerical calculation in the actual engineering. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly and intuitively understand the related principle content of the application, the following figures are attached for easy understanding.

[0033] Fig. 1 is a schematic view of the relationship between the coordinate system and the d-q coordinate system established in the application;

[0034] Fig. 2 is a schematic view of the relationship between the d-axis current i d , the q-axis current i q and the stator current vector i s in the maximum torque current ratio;

[0035] Fig. 3 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 application;

[0036] Fig. 4(a) is a simulation effect diagram of the d-axis current obtained by using the control method of the application when the motor speed is 1500r / min;​

[0037] Figure 4(b) is a simulation result of the d-axis current obtained by using the traditional vector control method when the motor speed is 1500 r / min in this invention;

[0038] Figure 4(c) is a simulation result of the difference between the 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.

[0039] Figure 5(a) is a simulation result of the q-axis current obtained by using the control method of the present invention when the motor speed is 1500 r / min.

[0040] Figure 5(b) is a simulation result of the q-axis current obtained by using the traditional vector control method when the motor speed is 1500 r / min in this invention;

[0041] Figure 5(c) is a simulation result 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; Figure 6(a) is a simulation result of the torque-current ratio obtained by the control method of the present invention when the motor speed is 1500 r / min.

[0042] Figure 6(b) is a simulation result of the torque-current ratio obtained by using the traditional vector control method when the motor speed is 1500 r / min in this invention;

[0043] Figure 6(c) is a simulation result of the difference between the torque-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.

[0044] Figure 7(a) is a simulation diagram of the d-axis current obtained by using the control method of the present invention when the motor speed is 2500 r / min.

[0045] Figure 7(b) is a simulation result of the d-axis current obtained by using the traditional vector control method when the motor speed is 2500 r / min in this invention;

[0046] Figure 7(c) is a simulation result of the difference between the 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.

[0047] Figure 8(a) is a simulation result of the q-axis current obtained by using the control method of the present invention when the motor speed is 2500 r / min.

[0048] Figure 8(b) is a simulation result of the q-axis current obtained by using the traditional vector control method when the motor speed is 2500 r / min in this invention;

[0049] Fig. 8(c) is a difference simulation effect diagram of q-axis current obtained by using the control method of the application and the traditional vector control method when the motor speed is 2500r / min in the application; Fig. 9(a) is a torque current ratio simulation effect diagram obtained by using the control method of the application when the motor speed is 2500r / min in the application;

[0050] Fig. 9(b) is a torque current ratio simulation effect diagram obtained by using the traditional vector control method when the motor speed is 2500r / min in the application;

[0051] Fig. 9(c) is a difference simulation effect diagram of torque current ratio obtained by using the control method of the application and the traditional vector control method when the motor speed of the application is 2500r / min. DETAILED DESCRIPTION

[0052] Combined with Figs. 1-3 of the application and the content of the application, a specific embodiment of the maximum torque current ratio control method of the surface-mounted permanent magnet motor based on the vector magnetic circuit is completed, and Figs. 4(a)-9(c) are simulation results of the specific implementation.

[0053] The electromagnetic torque equation and the maximum torque current ratio control method of the surface-mounted permanent magnet motor based on the vector magnetic path provided by the application include the following steps:

[0054] Step 1: Establish the d-axis and q-axis vector magnetic circuit model of the surface-mounted permanent magnet motor, and regard the inverse tangent value of the equivalent magnetic reactance and the magnetic resistance as the iron loss angle δ, and use the iron loss angle to induce the influence of the eddy current and the magnetic hysteresis effect on the electromagnetic torque;

[0055] Introduce the magnetic inductance and the magnetic capacity C two vector magnetic circuit parameters into the d-axis and q-axis magnetic circuit model of the surface-mounted permanent magnet motor, and construct the d-axis and q-axis vector magnetic circuit model, which uses the magnetic inductance and the magnetic capacity C to represent the size of the eddy current and the magnetic hysteresis effect induced by the iron loss; the magnetic inductance and the magnetic capacity C both make the magnetic flux lag behind the magnetomotive force or the current, so the equivalent magnetic inductance parameter equivalent magnetic inductance and the magnetic capacity C have the same effect; in the d-axis and q-axis vector magnetic circuit model, the angle at which the magnetic flux lags behind the magnetomotive force or the current is the iron loss angle δ, which can be expressed as:

[0056] Let

[0057] k is called the equivalent magnetic inductance parameter, which can be measured by experiment, and in the application, the change of the equivalent magnetic inductance coefficient is not considered, and the equivalent magnetic inductance coefficient is regarded as a fixed parameter; since the magnetic resistance is expressed as The iron loss angle of a surface-mounted permanent magnet motor is expressed as: δ=arctan(ωL) s k) (3)

[0058] In equations (1)-(3), Let C be the magnetic induction in the dq coordinate system, and C be the magnetic capacitance in the dq coordinate system. The equivalent magnetic field in the dq coordinate system. Let L be the reluctance in the dq coordinate system. s Let be the inductance in the dq coordinate system, k be the equivalent magnetic flux density, δ be the iron loss angle, ω be the rotor electric angular velocity, and N be the number of turns in the armature winding.

[0059] Step 2: Introduce equivalent magnetic induction parameters into the d-axis and q-axis magnetic circuit equations of the surface-mount permanent magnet motor. After performing a coordinate transformation, we obtain the magnetic circuit equations along the d-axis and q-axis in the dq coordinate system:

[0060] In equation (4), and Let Φ be the d-axis magnetomotive force and the q-axis magnetomotive force in the dq coordinate system. d and Φ q Let i be the magnetic flux along the d-axis and the magnetic flux along the q-axis in the dq coordinate system. d and i q Let d be the d-axis current and q-axis current in the dq coordinate system. For the reluctance in the dq coordinate system, L is the equivalent magnetic field in the dq coordinate system. s Let ψ be the inductance in the dq coordinate system. f ω is the permanent magnet flux linkage, ω is the electric angular velocity of the rotor, and p is the differential operator.

[0061] When the motor is running stably, the magnetic circuits of the d-axis and q-axis are assumed to be in a stable state. Further, we can obtain:

[0062] Combining equations (3) and (5), we can obtain the flux linkage equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit in the dq coordinate system:

[0063] Furthermore, multiplying both sides of equation (6) by cosδ, we get:

[0064] In equation (7), The coordinate transformation matrix is ​​the matrix that rotates the dq coordinate system in the hysteresis direction by the iron loss angle δ, resulting in... The coordinate system is shown in Figure 1.

[0065] In equation (5-7), ψ d and ψ q Let i be the d-axis flux linkage and q-axis flux linkage in the dq coordinate system. d and i q Let L be the d-axis current and q-axis current in the dq coordinate system. s Let ψ be the inductance in the dq coordinate system. f ω is the flux linkage of the permanent magnet, and ω is the electric angular velocity of the rotor.

[0066] The d-axis and q-axis voltages (magnetic flux linkages) are transformed by the coordinate transformation matrix M. δ After transformation, we get shaft and The shaft voltage (magnetic flux linkage), further derived from equation (7), can be obtained based on the vector magnetic circuit and The flux linkage equation of a surface-mounted permanent magnet motor in coordinate system:

[0067] Voltage equations for a surface-mounted permanent magnet motor in coordinate system:

[0068] Furthermore, based on the relationship And equation (8), replacing the d-axis and q-axis currents. shaft and shaft current, then shaft and Substituting the axial flux linkage, we obtain from equation (9):

[0069] Because of R s sinδ<<ωL s cosδ, ignoring R in equation (10) s sinδ, according to equation (10), is derived based on the vector magnetic circuit and Voltage equations for a surface-mounted permanent magnet motor in a coordinate system:

[0070] Multiply by the left side on both sides of equation (8). The inverse matrix M of the coordinate transformation matrix δ -1 The flux linkage equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit in the dq coordinate system is obtained as follows:

[0071] Equation (8-12), ψ d and ψ q Let the magnetic flux linkage be in the dq coordinate system. and for coordinate system shaft flux and Axial magnetic flux, and for coordinate system shaft voltage and shaft voltage, and for coordinate system shaft current and shaft current, i d and i q Let L be the current in the dq coordinate system. s Let R be the inductance in the dq coordinate system. s Let ψ be the resistance in the dq coordinate system. f δ is the permanent magnet flux linkage, ω is the iron loss angle, ω is the electric angular velocity of the rotor, and p is the differential operator.

[0072] 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:

[0073] Electromagnetic torque equation of a surface-mounted permanent magnet motor in the dq coordinate system, neglecting eddy current and hysteresis effects:

[0074] Substituting the d-axis and q-axis flux linkages based on the vector magnetic circuit, i.e., equation (12), into equation (13), we obtain the electromagnetic torque equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit in the dq coordinate system, considering eddy current and hysteresis effects:

[0075] The electromagnetic torque equation of the surface-mount permanent magnet motor based on vector magnetic circuit proposed in this invention includes d-axis and q-axis current components. Therefore, the maximum torque-to-current ratio control method requires finding the optimal combination of quadrature and direct-axis currents under the current operating condition, as expressed below:

[0076] As shown in Figure 2, the relationship between the stator current vector and the quadrature and direct-axis currents can be expressed as:

[0077] Substituting equation (16) into equation (15), we obtain the relationship between electromagnetic torque and stator current vector angle:

[0078] The stator current vector i in equation (17) s After phase shifting, the expression for the electromagnetic torque per unit current is obtained:

[0079] The maximum unit current electromagnetic torque is obtained when the derivative of the unit current electromagnetic torque to the stator current vector angle is equal to zero, and the motor operating point corresponding to the stator current vector angle at this time is the MTPA (Maximum Torque per Ampere) control point, which is specifically expressed as:

[0080] Further, the following is obtained:

[0081] Further, the motion equation of the surface-mounted permanent magnet motor is obtained:

[0082] In formula (13-21), ψ d and ψ q are fluxes in the d-q coordinate system, L s is inductance in the d-q coordinate system, i d and i q are currents in the d-q coordinate system, i s is a stator current vector in the d-q coordinate system, β is an angle between i s and the d-axis, ψ f is a permanent magnet flux, p n is the number of motor pole pairs, δ is an iron loss angle, ω is an electrical angular velocity of the rotor, J is a moment of inertia, T e is an electromagnetic torque of the surface-mounted permanent magnet motor in the d-q coordinate system without considering eddy current and magnetic hysteresis effects, T δ is an electromagnetic torque of the surface-mounted permanent magnet motor based on the vector magnetic circuit in the d-q coordinate system considering eddy current and magnetic hysteresis effects, T L is a load torque, and B is a damping coefficient of the motor.

[0083] Step 4: Establish a maximum torque current ratio control method of the surface-mounted permanent magnet motor based on the vector magnetic circuit:

[0084] As shown in FIG. 3, the three-phase currents of the surface-mounted permanent magnet motor are sampled to obtain sampling values i a * , i b * , i c * , i a * , i b * , and i c * ; d * , and i q * are obtained through coordinate transformation;

[0085] Rotor electrical angular velocity ω and rotor electrical angular velocity setpoint ω * The error is processed by a PI controller to obtain the stator current vector i. s The d-axis and q-axis current setpoints i are obtained by relating the stator current vector to the quadrature and direct-axis currents. d and i q Specifically: i q =f1(i s ) = i s sinβ i d =f2(i s ) = i s cosβ

[0086] will i d * and i q * With setting value i d and i q The errors are input into two PI controllers respectively, and the results are obtained. Voltage setpoint in coordinate system and Will and Through coordinate transformation matrix M δ Inverse transformation yields the voltage setpoint u in the dq coordinate system. d and u q By performing an inverse Park transformation, the voltage setpoint u in the dq coordinate system is then... d and u q The voltage setpoint u in the α-β coordinate system is obtained by transformation. α and u β , use u α and u β The synthesized voltage space vector is modulated by the input voltage space vector modulation module SVPWM, and the output state code values ​​of the three half-bridges at that moment are used to control the switching of the MOSFETs of the three-phase inverter to control the motor.

[0087] Vector control simulation was performed on a surface-mounted permanent magnet motor. First, the motor speed was adjusted to 1500 r / min with a load of 5 N·m. Then, the motor speed was increased to 2500 r / min, while the load remained at 5 N·m. The changes in the d-axis and q-axis currents, as well as the torque-to-current ratio, were observed. The motor model and control method used in this invention were compared with those of a traditional motor model. d The effectiveness of the control method with a value of 0 was evaluated; the influence of iron loss on motor control performance at different speeds was compared to verify the feasibility of the electromagnetic torque equation based on vector magnetic circuit and the maximum torque-current ratio of the surface-mounted permanent magnet motor proposed in this invention. The parameters of the surface-mounted permanent magnet motor in the simulation are shown in Table 1.

[0088] Table 1 Parameters of surface-mounted permanent magnet motor in simulation

[0089] As shown in Figs. 4(a)-5(c) and Figs. 7(a)-8(c), the currents of d-axis and q-axis in the control method of the application are higher than those in the conventional vector control, and it can be seen that in actual motor working conditions, the eddy current and hysteresis effect have a hindering effect on the current, indicating the correctness of the motor model established in the application and the electromagnetic torque equation proposed.

[0090] As shown in Figs. 6(a)-6(c) and Figs. 9(a)-9(c), the torque current ratio of the motor at a speed of 2500 r / min is smaller than that at 1500 r / min, and it can be seen that at the same load torque, the higher the speed, the greater the hindering effect of the eddy current and hysteresis effect on the current, and the greater the influence on the motor performance, which is of great significance for accurate control of the output torque in actual operation.

Claims

1. An electromagnetic torque equation of a vector-magnetic-path-based electric machine, characterized by, The electromagnetic torque equation of the surface-mounted permanent magnet motor based on the vector magnetic circuit considering eddy current and magnetic hysteresis effect in d-q coordinate system is expressed as follows: where i d and i q are the d-axis and q-axis currents, L s is the inductance in d-q frame, ψ f is the permanent magnet flux linkage, p n is the number of pole pairs, δ is the iron loss angle, T δ is the electromagnetic torque of surface-mounted permanent magnet machines based on vector magnetic potential considering eddy current and hysteresis effects in d-q frame.

2. A method for calculating maximum torque per ampere ratio of a vector flux based electric machine characterized by, Based on the electromagnetic torque equation of the vector-magnetic-path-based electric machine as claimed in claim 1, the maximum torque current ratio is calculated as follows: The relationship of the stator current vector and the cross-axis and direct-axis currents is expressed as: Among them, i d and i q Let i be the d-axis current and q-axis current in the dq coordinate system. s Let β be the stator current vector in the dq coordinate system, and let β be the stator current vector angle, i being the stator current vector. s The angle between ψ and the d-axis f For permanent magnet flux linkage, p n δ represents the number of pole pairs of the motor and the iron loss angle.

3. The method of claim 2, wherein the maximum torque per ampere ratio of the vector-magnetic-path-based electric machine is calculated by: ###0002### where, Tm is the maximum torque of the electric machine, I is the maximum current of the electric machine, and φ is the maximum flux of the electric machine. Substituting equation (3) into the electromagnetic torque equation in equation (2), the electromagnetic torque T is obtained δ The relationship with the stator current vector angle β is: Stator current vector i s After the phase-shifting, the expression of the unit current electromagnetic torque F(β) is further obtained as: The relationship must be satisfied when the unit current electromagnetic torque F(β) is maximum: Further, it is found that:

4. The method of claim 1 or 2, wherein, Introducing magnetic induction and magnetic capacity C two vector magnetic circuit parameters in d-axis and q-axis vector magnetic circuit model of surface-mounted permanent magnet motor, magnetic induction and magnetic capacity C both make the magnetic flux lag behind the magnetic motive force or current, the angle of the magnetic flux lagging behind the magnetic motive force or current is the iron loss angle δ, which is expressed as: Let k is called an equivalent magnetic induction parameter; Since the magnetic reluctance is expressed as The iron loss angle δ of the surface-mounted permanent magnet motor is expressed as: δ = arctan(ωL s k) (3) Bd is the magnetic induction in the d-axis coordinate system, Bdq is the magnetic induction in the d-q coordinate system, C is the magnetic capacity in the d-q coordinate system, and for the equivalent magnetic induction in the d-q coordinate system, L is the reluctance in the d-q coordinate system s L is the inductance in the d-q coordinate system, k is the equivalent magnetic permeability, 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 of claim 2, wherein the maximum torque per ampere ratio of the vector magnetic circuit-based motor is calculated by: Voltage equation of surface-mounted permanent magnet motor based on vector magnetic circuit: wherein, and For Voltage in the d-q coordinate system, i d and i q Current in the d-q coordinate system, L s Inductance in the d-q coordinate system, R s Resistance in the d-q coordinate system, ψ f Permanent magnet flux linkage, δ is the iron loss angle, ω is the electrical angular velocity of the rotor, and p is the differential operator.

6. The method of claim 5, wherein the maximum torque per ampere ratio of the vector-magnetic-path-based electric machine is calculated by: The relationship between the voltage in the coordinate system and the voltage in the d-q coordinate system is as follows: where M δ is a coordinate transformation matrix, represented as:

7. A method of controlling a motor based on a vector magnetic circuit, characterized by, The method comprises the following steps: Sampling the three-phase current of the surface-mounted permanent magnet motor to obtain a sampling value i a * 、 b * 、 c * , a * 、 b * 、 c * , d * and i q * ; rotor electrical angular velocity ω * The error between the rotor electrical angular velocity set value ω and the rotor electrical angular velocity ω is subjected to a PI controller to obtain a stator current vector i s The d-axis and q-axis current set values i d and i q Specifically, i q = i s sin β i d = i s cosβ β represents a stator current vector angle, and δ represents an iron loss angle; The current sampling value i in the d-q coordinate system is converted into the α-β coordinate system, and the current sampling value i in the α-β coordinate system is converted into the d-q coordinate system. d * And the error of i q * and the set value i d and i q The errors are respectively input into two PI controllers to obtain Voltage setpoint in a coordinate system and Will and Through the coordinate transformation matrix M δ The inverse transformation obtains the voltage setting value u in the d-q coordinate system d And u q , through the inverse Park transformation, and then the voltage setting value u in the d-q coordinate system d And u q The transformation obtains the voltage setting value u in the α-β coordinate system α And u β , u α And u β Synthesize the voltage space vector, input the voltage space vector modulation module for modulation, output the state code value of three half bridges, control the MOS tube switching of the three-phase inverter to control the motor.

8. The method of claim 7, wherein, The motor operating point corresponding to the stator current vector angle β is an MTPA control point.

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