A method for flux-weakening and mode switching control of a permanent magnet synchronous motor

Abstract

The application discloses a weak magnetic and mode switching control method of a permanent magnet synchronous motor and relates to the technical field of motor control, which comprises the following steps: obtaining the d-axis voltage, q-axis voltage, d-axis current, q-axis current, DC bus voltage and maximum torque current angle of a permanent magnet synchronous motor stator; determining whether conditions one and two are met; when the conditions one and two are both met, switching the operation mode of the permanent magnet synchronous motor to a weak magnetic region single current regulator weak magnetic control mode based on voltage phase angle; when the conditions one and two are both not met, switching the operation mode of the permanent magnet synchronous motor to a constant torque region double current regulator control mode; when only one of the conditions one and two is met, keeping the current operation mode of the permanent magnet synchronous motor; thereby, the weak magnetic control based on voltage phase angle and the smooth switching of the weak magnetic region and the constant torque region can be realized, and the influence of weak magnetic region cross coupling can be avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of motor control, in particular to a method for field weakening and mode switching control of a permanent magnet synchronous motor. BACKGROUND

[0002] Since the magnetic field generated by the permanent magnet of the permanent magnet synchronous motor (PMSM) is fixed and cannot be adjusted, when the motor terminal voltage reaches the maximum voltage output by the driver, the operating speed cannot continue to rise, and in order to further improve the speed, field weakening control must be performed. The existing permanent magnet synchronous motor field weakening control algorithms include formula calculation method, table lookup method, negative direct-axis current compensation method, voltage feedback method, etc.

[0003] The existing permanent magnet synchronous motor field weakening control algorithm is based on field orientation, and has two current regulators, which respectively control the direct-axis current i d and the quadrature-axis current i q When the motor enters the field weakening control, as the speed ω e increases, the amplitude of the cross-axis voltage and ω e related term in the motor voltage dynamic equation becomes larger, but at this time the voltage amplitude is already greater than the maximum value of the inverter output voltage, which causes the current regulator to be easily saturated and affect the motor performance, and even cause instability Therefore, it is impossible to simultaneously meet the regulation requirements of the d-axis and q-axis current regulators.

[0004] And there is cross coupling between the two current regulators, as shown in the formula: Where, i d , i q are the PMSM stator d-axis and q-axis currents; L d , L q are the PMSM stator d-axis and q-axis inductances; ω e is the electrical angular velocity; is the permanent magnet flux linkage. According to the above formula, the d-axis voltage u d and the q-axis voltage u q exist cross coupling related to the angular velocity ω e , so as to affect the stability and deep field weakening ability of the traditional double current regulator field weakening control structure. SUMMARY

[0005] The purpose of the present application is to provide a method for field weakening and mode switching control of a permanent magnet synchronous motor, which can realize field weakening control based on voltage phase angle, and smooth switching between the field weakening region and the constant rotation region, while avoiding the influence of cross coupling in the field weakening region.

[0006] To achieve the above purpose, the present application provides the following solutions:

[0007] A method for field weakening and mode switching control of a permanent magnet synchronous motor, the control method comprising:

[0008] obtaining a d-axis voltage u d , a q-axis voltage u q , a d-axis current i d , a q-axis current i q , a DC bus voltage u dc , and a maximum torque current ratio angle θ M ;

[0009] determining whether the following conditions are met according to the d-axis voltage u d , the q-axis voltage u q , the d-axis current i d , the q-axis current i q , the DC bus voltage u dc , and the maximum torque current ratio angle θ M :

[0010] Condition one: wherein u s is a voltage vector, and u max is a maximum output voltage of an inverter;

[0011] Condition two: i d <-abs(i q ) tan θ M ; wherein abs() is an absolute value function;

[0012] when both the condition one and the condition two are met, switching an operating mode of the permanent magnet synchronous motor to a field weakening region voltage phase angle based single current regulator field weakening control mode;

[0013] when both the condition one and the condition two are not met, switching the operating mode of the permanent magnet synchronous motor to a constant torque region double current regulator control mode;

[0014] when only one of the condition one and the condition two is met, maintaining a current operating mode of the permanent magnet synchronous motor; the operating mode is either the field weakening region voltage phase angle based single current regulator field weakening control mode or the constant torque region double current regulator control mode.

[0015] Optionally, the switching the permanent magnet synchronous motor to the field weakening region voltage phase angle based single current regulator field weakening control mode specifically comprises:

[0016] obtaining an electromagnetic torque T e according to an electromagnetic torque equation one;

[0017] the electromagnetic torque equation one is:

[0018]

[0019] wherein T e is the electromagnetic torque, p is the number of motor pole pairs, is the permanent magnet flux linkage, L d is the stator d-axis inductance of the permanent magnet synchronous motor, L q is the stator q-axis inductance of the permanent magnet synchronous motor;

[0020] According to the electromagnetic torque T e , the amplitude of the stator current vector is determined;

[0021] According to the amplitude of the stator current vector and the q-axis current i q , the d-axis dynamic current i is determined by using the electromagnetic torque equation two;

[0022] The electromagnetic torque equation two is:

[0023] The difference between the d-axis dynamic current i and the d-axis current i d is calculated, and the difference is input to a PI current regulator;

[0024] An adjusted output is obtained by the PI current regulator, and the voltage phase angle β is obtained; the voltage phase angle β is the included angle between the voltage vector u s and the d-axis voltage u d ;

[0025] According to the inverter maximum output voltage u max and the voltage phase angle β, the current d-axis voltage u d and the q-axis voltage u q are obtained;

[0026] The current d-axis voltage u d and the q-axis voltage u q are input to the motor control system of the permanent magnet synchronous motor, so that the motor control system of the permanent magnet synchronous motor operates in the voltage phase angle-based single current regulator flux-weakening control mode in the flux-weakening region.

[0027] Optionally, the current d-axis voltage u d and the q-axis voltage u q are determined according to the following formula:

[0028]

[0029] Optionally, the stable operation range of the voltage phase angle-based single current regulator flux-weakening control mode is [π / 2, π].

[0030] Optionally, when the permanent magnet synchronous motor is in a field weakening region and operates in a voltage phase angle based single current regulator field weakening control mode, the permanent magnet synchronous motor is further connected with a low pass filter, through which a q-axis current i q .

[0031] Further, the constant torque region double current regulator control mode comprises:

[0032] The motor control system of the permanent magnet synchronous motor is subjected to position detection, and a motor electrical angle θ is obtained through a motor position sensor, and speed calculation is performed according to the motor electrical angle θ to obtain an actual speed ω;

[0033] According to a dynamic speed ω * sent by an upper computer or an upper layer control unit, a difference between the dynamic speed ω * and the actual speed ω is calculated to obtain a first difference, and the first difference is input into a PI speed regulator to obtain a stator current vector

[0034] A maximum torque current ratio control strategy MTPA algorithm is used to obtain a d-axis dynamic current id , a q-axis dynamic current iq and a q-axis dynamic current iq

[0035] A difference between the d-axis dynamic current id and a d-axis current id d is calculated to obtain a second difference, and the second difference is input into a first PI current regulator to obtain a current d-axis voltage u d ;

[0036] A difference between the q-axis dynamic current iq and a q-axis current iq q is calculated to obtain a third difference, and the third difference is input into a second PI current regulator to obtain a current q-axis voltage u q ;

[0037] The current d-axis voltage u d and the current q-axis voltage u q are subjected to coordinate transformation to obtain an α-axis voltage u α and a β-axis voltage u β ;

[0038] The α-axis voltage u α and the β-axis voltage u β are modulated through a voltage space vector pulse width modulation SVPWM method to obtain an action time of an inverter three-phase voltage, and are input into the inverter;

[0039] According to the acting time of the three-phase voltage of the inverter, the pulse width modulation wave opening time of the three-phase bridge arm of the inverter is controlled to obtain three-phase voltage, and motor phase current i a , motor phase current i b , and motor phase current i c ;

[0040] The motor phase current i a , i b , and i c are input to the motor control system, so that the permanent magnet synchronous motor operates in a constant torque area double current regulator control mode.

[0041] Further, when the permanent magnet synchronous motor operates in the constant torque area double current regulator control mode, the motor phase current i a and the motor phase current i b input to the permanent magnet synchronous motor control system are obtained by a current sensor, and coordinate transformation is performed to obtain the d-axis current i d , the q-axis current i q .

[0042] According to the specific embodiments provided by the application, the following technical effects are disclosed:

[0043] The weak magnetic and mode switching control method of the permanent magnet synchronous motor adopts a single current regulator weak magnetic control mode based on voltage phase angle in a weak magnetic area and a constant torque area double current regulator control mode, and the switching or retention of the operating mode is determined by comparing the obtained d-axis voltage u d , q-axis voltage u q , d-axis current i d , q-axis current i q , DC bus voltage u dc , and maximum torque current angle θ M with conditions one and two, so that the weak magnetic control based on voltage phase angle and the smooth switching of the weak magnetic area and the constant torque area can be realized, and the influence of cross-coupling in the weak magnetic area is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0045] Figure 1 The flowchart of the weak magnetic and mode switching control method of the permanent magnet synchronous motor;

[0046] Figure 2 Voltage phase angle diagram for permanent magnet synchronous motor;

[0047] Figure 3 Voltage phase angle based single current regulator flux weakening control mode diagram;

[0048] Figure 4 Equal torque curve diagram;

[0049] Figure 5 Stable operation range diagram for single current regulator flux weakening control mode;

[0050] Figure 6 Switching control logic and flux weakening flag (FLAG) change diagram;

[0051] Figure 7 Constant torque region double current regulator control mode diagram. DETAILED DESCRIPTION

[0052] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0053] The purpose of the present application is to provide a flux weakening and mode switching control method for permanent magnet synchronous motor, which can realize voltage phase angle based flux weakening control and smooth switching between flux weakening region and constant torque region, and avoid the influence of flux weakening region cross coupling.

[0054] According to the steady-state mathematical model of permanent magnet synchronous motor in the rotor synchronous rotating coordinate system in the flux weakening region:

[0055]

[0056] Where, i d , i q are PMSM stator d, q axis currents; L d , L q are PMSM stator d, q axis inductances; ω e is the electrical angular velocity; is the permanent magnet flux linkage; u max is the maximum output voltage of the inverter; u dc is the DC bus voltage.

[0057] Where, according to the first and second equations of the steady-state mathematical model in the flux weakening region: d-axis voltage u d and q-axis voltage u qThere is a cross coupling related to angular velocity ω e , thus affecting the stability and deep flux-weakening capability of the conventional dual current regulator flux-weakening control structure.

[0058] It can be seen from the third formula that: after entering the flux-weakening region, the voltage vector u s saturates to the maximum output voltage u max of the inverter.

[0059] It can be seen from the fourth and fifth formulas that: according to the voltage phase angle control idea, after entering the flux-weakening region, the d-axis voltage u d and the q-axis voltage u q can be represented by the voltage vector u s and the voltage phase angle β.

[0060] Since the value of the voltage vector u s at this time is equal to the fixed value u max , the d-axis voltage u d and the q-axis voltage u q are only adjusted by one variable, the voltage phase angle β.

[0061] Therefore, the present application establishes a single current regulator flux-weakening control mode based on the voltage phase angle in the flux-weakening region (as shown in Figure 3 ), while retaining the dual current regulator control mode in the constant torque region (as shown in Figure 7 ).

[0062] In order to make the above-mentioned purposes, characteristics and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below in combination with the drawings and specific embodiments.

[0063] As shown in Figure 1 , the flux-weakening and mode switching control method of the permanent magnet synchronous motor of the present application comprises:

[0064] Step S1: obtaining the d-axis voltage u d , the q-axis voltage u q , the d-axis current i d , the q-axis current i q , the DC bus voltage u dc , and the maximum torque current ratio angle θ M .

[0065] Step S2: determining whether the following conditions are met according to the d-axis voltage u d , the q-axis voltage u q , the d-axis current i d , the q-axis current i q , the DC bus voltage u dc , and the maximum torque current ratio angle θ M .

[0066] Condition one: Among them, u s For voltage vector, u max This is the maximum output voltage of the inverter;

[0067] Condition 2: i d <-abs(i q )tanθ M ; where abs() is the absolute value function.

[0068] Step S3: When both conditions one and two are met, switch the operating mode of the permanent magnet synchronous motor to the field weakening control mode based on voltage phase angle of the field weakening zone using a single current regulator.

[0069] Step S4: When neither condition one nor condition two is satisfied, switch the operating mode of the permanent magnet synchronous motor to the constant torque zone dual current regulator control mode.

[0070] Step S5: If only one of the conditions one and two is met, the current operating mode of the permanent magnet synchronous motor is maintained; the operating mode is the field weakening control mode based on voltage phase angle of the field weakening zone with a single current regulator, or the constant torque zone with a dual current regulator control mode.

[0071] In step S3, switching the operating mode of the permanent magnet synchronous motor to the field weakening control mode based on voltage phase angle using a single current regulator in the field weakening zone specifically includes:

[0072] Step S31: Obtain the electromagnetic torque T according to the first electromagnetic torque equation. e .

[0073] The first electromagnetic torque equation is:

[0074]

[0075] Among them, T e Where p is the electromagnetic torque and p is the number of pole pairs of the motor. For permanent magnet flux linkage, L d For PMSM stator d-axis inductance, L q This is the q-axis inductor of the PMSM stator.

[0076] Step S32: Based on the electromagnetic torque T e Determine the stator current vector This makes the current operating point follow the constant torque curve (the constant torque curve is...). Figure 4 (The solid line in the image). At this time, the stator current vector... Amplitude and electromagnetic torque T e Equal in magnitude, replacing T in the electromagnetic torque equation e .

[0077] Step S33: Based on the stator current vector The amplitude and q-axis current i q The dynamic current along the d-axis is determined using the second electromagnetic torque equation.

[0078] The second electromagnetic torque equation is:

[0079] Step S34: Calculate the d-axis dynamic current With d-axis current i d The difference is calculated and then input to the PI current regulator.

[0080] Step S35: Adjust the output through the PI current regulator to obtain the voltage phase angle β; the voltage phase angle β is the voltage vector u s With d-axis voltage u d The included angle.

[0081] As can be seen from steps S34-S35, the voltage phase angle β changes with the dynamic current along the d-axis. With d-axis current i d It changes according to the adjustment.

[0082] Step S36: Based on the inverter's maximum output voltage u max The current d-axis voltage u is obtained from the voltage phase angle β. d and q-axis voltage u q .

[0083] Specifically, the current d-axis voltage u is determined according to the following formula. d and q-axis voltage u q (like Figure 2 As shown):

[0084]

[0085] Step S36: Set the current d-axis voltage u d and q-axis voltage u q The input is sent to the motor control system of the permanent magnet synchronous motor, so that the motor control system of the permanent magnet synchronous motor operates in the field weakening region in the single current regulator field weakening control mode based on voltage phase angle.

[0086] The single-current regulator field weakening control mode based on voltage phase angle has been established. After entering the field weakening region, the single-current regulator field weakening control mode has only one PI current regulator. The PI current regulator adjusts the output voltage phase angle β, and the PI current regulator adjusts the d-axis voltage u by adjusting the voltage phase angle β. d and q-axis voltage u qThis solves the problems of poor system stability and insufficient deep field weakening capability caused by cross-coupling in the dual current regulator field weakening control structure.

[0087] To ensure stable operation of the single-current regulator's field weakening control mode, it is necessary to determine the stable operating range of the single-current regulator's field weakening control mode, namely... Figure 3 The stable operating range of the PI current regulator: Analysis using small-signal modeling and the Routh criterion yields the following results. The stable operating range of the field weakening control mode based on voltage phase angle single current regulator is: (like Figure 5 (The point area shown).

[0088] Therefore, after entering the weak magnetic region, the output range of the PI current regulator is The range of values ​​for the voltage phase angle β is: Once the voltage phase angle β is determined, the current d-axis voltage u can then be determined. d and q-axis voltage u q This completes the closed-loop control of the motor and enables stable operation in the weak magnetic region.

[0089] Preferably, when the permanent magnet synchronous motor operates in the field weakening region using a single current regulator field weakening control mode based on voltage phase angle, the permanent magnet synchronous motor is also connected to a low-pass filter (LFP) to obtain the q-axis current i through the LFP. q .

[0090] Since the single-current regulator field weakening control mode is only suitable for permanent magnet synchronous motors operating in the field weakening region and not for constant torque region operation, the traditional dual-current regulator control is still used in the constant torque region. Therefore, it is necessary to design a switching method for different control structures (such as...). Figure 7 (As shown).

[0091] In step S4, switching the operating mode of the permanent magnet synchronous motor to the constant torque region dual current regulator control mode specifically includes:

[0092] Step S41: Perform position detection on the motor control system of the permanent magnet synchronous motor, obtain the motor electrical angle θ through the motor position sensor, and calculate the speed based on the motor electrical angle θ to obtain the actual rotational speed ω.

[0093] Step S42: Based on the dynamic speed ω sent by the host computer or upper-level control unit * Calculate the dynamic rotational speed ω * The difference between the actual rotational speed ω and the actual rotational speed ω is used to obtain a first difference value, which is then input into the PI speed regulator to obtain the stator current vector.

[0094] Step S43: Using the Maximum Torque-to-Current Ratio (MTPA) control strategy algorithm, based on the stator current vector... Obtain the d-axis dynamic current and q-axis dynamic current

[0095] Step S44: Calculate the d-axis dynamic current With d-axis current i d The difference is used to obtain a second difference, which is then input to the first PI current regulator to obtain the current d-axis voltage u. d .

[0096] Step S45: Calculate the q-axis dynamic current With q-axis current i q The difference is used to obtain a third difference, which is then input to the second PI current regulator to obtain the current q-axis voltage u. q .

[0097] Step S46: For the current d-axis voltage u d and the current q-axis voltage u q Perform coordinate transformation to obtain the α-axis voltage u. α and β-axis voltage u β .

[0098] Step S47: The α-axis voltage u is adjusted using the Voltage Space Vector Pulse Width Modulation (SVPWM) method. α and β-axis voltage u β The modulation is performed to obtain the duration of the three-phase voltage of the inverter, and then input to the inverter.

[0099] Based on the duration of the three-phase voltage of the inverter, the pulse width modulation (PWM) wave on-time of the three-phase bridge arms of the inverter is controlled to obtain the three-phase voltage and generate the motor phase current i. a Motor phase current i b and motor phase current i c ;

[0100] The motor phase current i a i b i c The input is sent to the motor control system of the permanent magnet synchronous motor, causing the motor control system of the permanent magnet synchronous motor to operate in the constant torque region dual current regulator control mode.

[0101] Furthermore, when the permanent magnet synchronous motor is operating in the constant torque region dual current regulator control mode, the motor phase current i input to the permanent magnet synchronous motor control system is obtained through a current sensor. a and motor phase current ib And coordinate transformation is carried out to obtain d-axis current i d , q-axis current i q .

[0102] Specifically, the control mode switching control logic and the field weakening flag FLAG are designed, and the change of the control mode switching control logic and the field weakening flag FLAG is as shown in the following table: Figure 6

[0103] (1) When both condition one (i.e. ①) and condition two (i.e. ②) are met, the field weakening flag is set to 1, and after the field weakening flag is set to 1, the PMSM adopts the single current regulator field weakening control mode based on voltage phase angle in the field weakening region (i.e. adopts the field weakening control structure as shown in the following table). Figure 3

[0104] (2) When neither condition one nor condition two is met, the field weakening flag is set to 0, and after the field weakening flag is set to 0, the PMSM adopts the double current regulator control mode in the constant torque region, and the d-axis voltage u d and the q-axis voltage u q are respectively obtained by the output of two PI current regulators (as shown in the following table). Figure 7

[0105] (3) When only one of the condition one and the condition two is met, the PMSM keeps the current operation mode unchanged.

[0106] The present application realizes the smooth switching of the constant torque region and the field weakening region of the permanent magnet synchronous motor through the switching of the MTPA control mode of the double current regulator and the single current regulator field weakening control mode.

[0107] In the specification, each embodiment is described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between each embodiment can be referred to each other. The principle and implementation manner of the present application are described by applying specific examples, and for the general technical personnel in the art, the specific implementation manner and application range will be changed according to the idea of the present application. In conclusion, the content of the specification should not be understood as the limitation of the present application.​​​

Claims

1. A method for flux-weakening and mode-switching control of a permanent magnet synchronous motor, characterized in that, The control method comprises: acquiring a d-axis voltage u of a stator of a permanent magnet synchronous motor d , a q-axis voltage u q , a d-axis current i d , a q-axis current i q , a direct current bus voltage u dc , and a maximum torque current angle θ M ; According to the d-axis voltage u d , the q-axis voltage u q , the d-axis current i d , the q-axis current i q , the DC bus voltage u dc , and the maximum torque current ratio angle θ M , it is determined whether the following condition is satisfied: Condition one: wherein u s is the voltage vector, u max is the maximum output voltage of the inverter; Condition two: i d <- abs(i q ) tan θ M ; wherein abs() is an absolute value function; When the condition one and the condition two are both satisfied, switching the operation mode of the permanent magnet synchronous motor to a field weakening region single current regulator voltage phase angle based field weakening control mode; When the condition one and the condition two are both not satisfied, switching the operation mode of the permanent magnet synchronous motor to a constant torque region double current regulator control mode; When only one of the condition one and the condition two is satisfied, maintaining the current operation mode of the permanent magnet synchronous motor; the operation mode is the field weakening region single current regulator voltage phase angle based field weakening control mode or the constant torque region double current regulator control mode.

2. The flux weakening and mode switching control method of the permanent magnet synchronous motor according to claim 1, characterized in that, The switching of the permanent magnet synchronous motor to the field weakening region single current regulator voltage phase angle based field weakening control mode specifically comprises: According to the electromagnetic torque equation one, the electromagnetic torque T e ; The electromagnetic torque equation one is: wherein T e is the electromagnetic torque, p is the number of motor pole pairs, is the permanent magnet flux linkage, L d is the stator d-axis inductance of the permanent magnet synchronous motor, L q is the stator q-axis inductance of the permanent magnet synchronous motor; According to the electromagnetic torque T e determining a stator current vector of the amplitude; According to the stator current vector the magnitude of the q-axis current i q , the d-axis dynamic current is determined using the electromagnetic torque equation two The electromagnetic torque equation two is: calculating the d-axis dynamic current the difference between the d-axis current i d and inputting the difference to a PI current regulator; The voltage phase angle β is an angle between a d-axis voltage u s and a q-axis voltage v d ​ According to the maximum output voltage u of the inverter max and the voltage phase angle β, the current d-axis voltage u d and the q-axis voltage u q ; The current d-axis voltage u d and q-axis voltage u q are input to the motor control system of the permanent magnet synchronous motor, so that the motor control system of the permanent magnet synchronous motor operates in the field weakening control mode based on the single current regulator field weakening control mode of the voltage phase angle.

3. The flux weakening and mode switching control method of the permanent magnet synchronous motor according to claim 2, characterized in that, The current d-axis voltage u is determined according to the following equation d and q-axis voltage u q :

4. The method of field weakening and mode switching control of permanent magnet synchronous motor according to claim 1, characterized in that, The stable operation range of the single current regulator voltage phase angle based field weakening control mode is [π / 2, π].

5. The method of field weakening and mode switching control of permanent magnet synchronous motor according to claim 1, characterized in that, When the permanent magnet synchronous motor is in a field weakening area and operates in a voltage phase angle-based single current regulator field weakening control mode, the permanent magnet synchronous motor is further connected with a low-pass filter, through which q-axis current i q .

6. The method of field weakening and mode switching control of a permanent magnet synchronous motor according to claim 1, wherein, The constant torque region double current regulator control mode comprises: The motor control system of the permanent magnet synchronous motor is subjected to position detection, the motor electric angle θ is obtained through a motor position sensor, and speed calculation is performed according to the motor electric angle θ to obtain an actual rotating speed ω. According to the dynamic rotating speed ω * sent by the host computer or upper control unit * , the difference between the dynamic rotating speed ω * and the actual rotating speed ω is calculated to obtain a first difference, and the first difference is input into a PI rotating speed regulator to obtain a stator current vector With the maximum torque per current control strategy MTPA algorithm, according to the stator current vector a d-axis dynamic current and a q-axis dynamic current calculating the d-axis dynamic current the difference between the d-axis current i d , obtaining a second difference value, and inputting the second difference value to a first PI current regulator to obtain a current d-axis voltage u d ; calculating the q-axis dynamic current the difference between the q-axis current i q , obtaining a third difference value, and inputting the third difference value to a second PI current regulator to obtain a current q-axis voltage u q ; performing coordinate transformation on the current d-axis voltage u d and the current q-axis voltage u q to obtain an α-axis voltage u α and a β-axis voltage u β ; The α-axis voltage u α and the β-axis voltage u β are modulated by a voltage space vector pulse width modulation (SVPWM) method to obtain the action time of the three-phase voltage of the inverter, and input to the inverter. According to the action time of the three-phase voltage of the inverter, the pulse width modulation wave opening time of the three-phase bridge arm of the inverter is controlled to obtain three-phase voltage, and motor phase current i is generated a , motor phase current i b , and motor phase current i c ; The motor phase currents i a , i b , i c are input to the motor control system, causing the permanent magnet synchronous motor to operate in a constant torque region dual current regulator control mode.

7. The method of field weakening and mode switching control of a permanent magnet synchronous motor according to claim 1, wherein, When the permanent magnet synchronous motor is in a constant torque region double current regulator control mode operation, the motor phase current i input to the permanent magnet synchronous motor control system is acquired by a current sensor a and the motor phase current i b is subjected to coordinate transformation to obtain a d-axis current i d and a q-axis current i q .

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