A control method, device, motor, storage medium and processor for a motor

Abstract

The present invention discloses a control method, device, motor, storage medium and processor for a motor. The method includes: in the field weakening control system of the motor, a single q-axis current regulator is adopted to freely switch between field weakening traction and braking control under field weakening conditions; in the control system of the single q-axis current regulator, a field weakening compensation module is added to perform field weakening compensation processing on the d-axis and q-axis currents of the motor; and an out-of-control limiting and compensation module is added to perform out-of-control limiting and compensation processing on the field weakening current of the motor to obtain the voltage vector angle of the field weakening control system of the motor; according to the voltage vector angle and the maximum stator voltage of the motor, the dq-axis reference voltage vector of the motor is determined to drive and control the system where the motor is located. With this solution, by adopting a single current loop control structure in the field weakening control of a permanent magnet synchronous motor and using a limiting method and a current compensation method for field weakening control, the stability of the control system of the permanent magnet synchronous motor can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of motors, and particularly relates to a control method, device, motor, storage medium and processor of a motor, and more particularly to a control method, device, motor, storage medium and processor of a permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motors have the advantages of high power density, simple structure and high operating efficiency, and are widely used in actual industrial applications. Considering the characteristics of actual application scenarios, permanent magnet synchronous motors often operate in a wide speed regulation range. As the speed of the permanent magnet synchronous motor increases, the back electromotive force of the permanent magnet synchronous motor will be limited by the voltage of the DC side of the inverter. In order to enable the permanent magnet synchronous motor to operate stably in a high-speed range, the permanent magnet synchronous motor must widen its speed regulation range through field weakening speed increase control. However, in related solutions, a dual current loop control method is adopted in the field weakening control of the permanent magnet synchronous motor. Affected by the dual-loop structure, there are output voltage amplitude saturation and cross-coupling phenomena in the two current regulators in the field weakening area. This adjustment conflict between current regulators will affect the motor performance, and in severe cases, it will cause the instability of the permanent magnet synchronous motor control system.

[0003] In the single current loop control of some solutions, when entering the deep field weakening area, there is also a possibility of current runaway, and in severe cases, it will also cause the instability of the permanent magnet synchronous motor system.

[0004] The above content is only used to assist in understanding the technical solution of the present invention, and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The object of the present invention is to provide a control method, device, motor, storage medium and processor of a motor, so as to solve the problem that the control system of the permanent magnet synchronous motor is unstable in the field weakening control of the permanent magnet synchronous motor, and achieve the effect of avoiding the instability of the permanent magnet synchronous motor control system and being beneficial to improving the reliability of the field weakening control of the permanent magnet synchronous motor by adopting a single current loop control structure in the field weakening control of the permanent magnet synchronous motor and adopting a limiting method and a current compensation method for field weakening control.

[0006] The present invention provides a control method for a motor, including: in the field-weakening control system of the motor, a single q-axis current regulator is adopted to freely switch between field-weakening traction and braking control under field-weakening conditions; in the control system of the single q-axis current regulator, a field-weakening compensation module is added to perform field-weakening compensation processing on the d-axis and q-axis currents of the motor; and an out-of-control limiting and compensation module is added to perform out-of-control limiting and compensation processing on the d-axis field-weakening current of the motor to obtain the voltage vector angle of the field-weakening control system of the motor; according to the voltage vector angle and the maximum stator voltage of the motor, the dq-axis reference voltage vector of the motor is determined, so as to perform drive control on the system where the motor is located according to the dq-axis reference voltage vector.

[0007] In some embodiments, in the control system of the single q-axis current regulator, a field-weakening compensation module is added to perform field-weakening compensation processing on the d-axis and q-axis currents of the motor; and an out-of-control limiting and compensation module is added to perform out-of-control limiting and compensation processing on the d-axis field-weakening current of the motor, including: in the field-weakening compensation module, dq-axis voltages are obtained according to the dq-axis currents after field-weakening, and then the dq-axis voltages are synthesized into a reference voltage amplitude, and after comparing and performing PI processing on the reference voltage amplitude with the maximum stator voltage of the motor, a field-weakening compensation current is obtained; d-axis current is obtained according to the q-axis current reference value of the motor, and the d-axis current is compensated by using the field-weakening compensation current to obtain a field-weakening current; in the out-of-control limiting and compensation module, the field-weakening current is clamped at a set characteristic current after being limited; as the speed of the motor increases, the field-weakening current is reduced to a set minimum value, and the q-axis current is reversely compensated to continue field-weakening.

[0008] In some embodiments, obtaining dq-axis voltages according to the dq-axis currents after field-weakening includes: obtaining the basic parameters of the motor; the basic parameters include at least one of three-phase current, rotor position, and speed; according to the basic parameters of the motor, dq-axis currents in the dq-axis system are obtained through coordinate transformation as the dq-axis currents after field-weakening; according to the dq-axis currents after field-weakening, dq-axis voltages are obtained through feedforward calculation; wherein, the dq-axis currents after field-weakening are the field-weakening currents after being limited by the out-of-control limiting and compensation module.

[0009] In some embodiments, obtaining d-axis current according to the q-axis current reference value of the motor includes: in the speed outer loop of the motor, comparing the actual speed of the motor with the reference speed and performing PI processing to obtain the q-axis current reference value of the motor; subjecting the q-axis current reference value of the motor to MTPA processing to obtain the d-axis current of the motor.

[0010] In some embodiments, after the field-weakening current is limited, it is clamped at a set characteristic current, including: the field-weakening current is the d-axis field-weakening current; the d-axis field-weakening current is limited by the set characteristic current to obtain the limited d-axis field-weakening current; the limited d-axis field-weakening current is restricted by the torque formula and the current limit circle to obtain the q-axis current value after field weakening.

[0011] In some embodiments, as the speed of the motor increases, the field-weakening current is reduced to a set minimum value, and the q-axis current is reversely compensated to continue field weakening, including: determining the difference between the d-axis field-weakening current before limiting and the d-axis field-weakening current after limiting, denoted as the first difference; compensating the d-axis field-weakening current after limiting with the first difference to continue field weakening; and adding the first difference to the q-axis current value after field weakening, comparing it with the actual q-axis current of the motor and performing PI processing to obtain the voltage vector angle of the motor; determining the d-axis field-weakening current after limiting and the q-axis current value after field weakening; performing feedforward calculation using the d-axis field-weakening current after limiting and the q-axis current value after field weakening to obtain the actual value of the stator voltage of the motor; correspondingly, according to the voltage vector angle and the maximum value of the stator voltage of the motor, determining the dq-axis reference voltage vector of the motor, including: combining the voltage vector angle of the motor with the maximum value of the stator voltage of the motor, and performing voltage amplitude operation to obtain the dq-axis reference voltage of the motor, so as to obtain the voltage vector angle of the field-weakening control system of the motor.

[0012] Matched with the above method, on the other hand, the present invention provides a control device for a motor, including: a control unit configured to adopt a single q-axis current regulator in the field-weakening control system of the motor to freely switch between field-weakening traction and braking control under field-weakening conditions; the control unit is further configured to add a field-weakening compensation module to the control system of the single q-axis current regulator to perform field-weakening compensation processing on the d-axis and q-axis currents of the motor; and add an out-of-control limiting and compensation module to perform out-of-control limiting and compensation processing on the d-axis field-weakening current of the motor to obtain the voltage vector angle of the field-weakening control system of the motor; the control unit is further configured to determine the dq-axis reference voltage vector of the motor according to the voltage vector angle and the maximum value of the stator voltage of the motor, so as to drive and control the system where the motor is located according to the dq-axis reference voltage vector.

[0013] In some embodiments, the control unit adds a field-weakening compensation module to the control system of the single q-axis current regulator to perform field-weakening compensation on the d-axis and q-axis currents of the motor; and adds an out-of-control limiting and compensation module to perform out-of-control limiting and compensation on the d-axis field-weakening current of the motor, including: in the field-weakening compensation module, obtaining the dq-axis voltage based on the dq-axis current after field-weakening, then synthesizing the reference voltage amplitude from the dq-axis voltage, and after comparing and performing PI processing on the reference voltage amplitude with the maximum stator voltage of the motor, obtaining the field-weakening compensation current; obtaining the d-axis current based on the q-axis current reference value of the motor, and compensating the d-axis current with the field-weakening compensation current to obtain the field-weakening current; in the out-of-control limiting and compensation module, the field-weakening current is clamped at a set characteristic current after limiting; as the speed of the motor increases, the field-weakening current is reduced to a set minimum value, and the q-axis current is reversely compensated to continue field-weakening.

[0014] In some embodiments, the control unit obtains the dq-axis voltage based on the dq-axis current after field-weakening, including: obtaining the basic parameters of the motor; the basic parameters include at least one of three-phase current, rotor position, and speed; based on the basic parameters of the motor, obtaining the dq-axis current in the dq-axis coordinate system through coordinate transformation as the dq-axis current after field-weakening; based on the dq-axis current after field-weakening, obtaining the dq-axis voltage through feed-forward calculation; wherein the dq-axis current after field-weakening is the field-weakening current after being limited by the out-of-control limiting and compensation module.

[0015] In some embodiments, the control unit obtains the d-axis current based on the q-axis current reference value of the motor, including: in the speed outer loop of the motor, comparing the actual speed of the motor with the reference speed and performing PI processing to obtain the q-axis current reference value of the motor; subjecting the q-axis current reference value of the motor to MTPA processing to obtain the d-axis current of the motor.

[0016] In some embodiments, the control unit clamps the field-weakening current at a set characteristic current after limiting, including: the field-weakening current is the d-axis field-weakening current; subjecting the d-axis field-weakening current to limiting by the set characteristic current to obtain the limited d-axis field-weakening current; subjecting the limited d-axis field-weakening current to the torque formula and current limit circle restriction to obtain the q-axis current value after field-weakening.

[0017] In some embodiments, as the rotational speed of the motor increases, the control unit reduces the field-weakening current to a set minimum value, performs reverse compensation on the q-axis current, and continues field weakening, including: determining the difference between the d-axis field-weakening current before limiting and the d-axis field-weakening current after limiting, denoted as the first difference; compensating the d-axis field-weakening current after limiting with the first difference and continuing field weakening; and adding the first difference to the q-axis current value after field weakening, comparing it with the actual q-axis current of the motor and performing PI processing to obtain the voltage vector angle of the motor; determining the d-axis field-weakening current after limiting and the q-axis current value after field weakening; performing feedforward calculation using the d-axis field-weakening current after limiting and the q-axis current value after field weakening to obtain the actual value of the stator voltage of the motor; correspondingly, the control unit determines the dq-axis reference voltage vector of the motor according to the voltage vector angle and the maximum stator voltage of the motor, including: combining the voltage vector angle of the motor with the maximum stator voltage of the motor, performing voltage amplitude operation to obtain the dq-axis reference voltage of the motor, so as to obtain the voltage vector angle of the field-weakening control system of the motor.

[0018] Matched with the above device, on the other hand, the present invention provides a motor, including: the control device of the motor described above.

[0019] Matched with the above method, on the other hand, the present invention provides a storage medium, the storage medium includes a stored program, wherein, when the program runs, it controls the device where the storage medium is located to execute the control method of the motor described above.

[0020] Matched with the above method, on the other hand, the present invention provides a processor, the processor is used to run a program, wherein, when the program runs, it executes the control method of the motor described above.

[0021] Thus, the solution of the present invention, by adopting a single q-axis current regulator in the field-weakening control method of a permanent magnet synchronous motor, can freely switch between traction and braking control under field-weakening conditions, and add a field-weakening current limiting module and a current compensation module to the control system of the single q-axis current regulator for limiting and current compensation; by adopting a single current loop control structure in the field-weakening control of a permanent magnet synchronous motor and adopting a limiting method and a current compensation method for field-weakening control, it can avoid the instability of the permanent magnet synchronous motor control system and is beneficial to improving the reliability of the field-weakening control of the permanent magnet synchronous motor.

[0022] Other features and advantages of the present invention will be described in the subsequent specification, and, partly, will become obvious from the specification, or will be understood by implementing the present invention.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0024] Figure 1 It is a schematic diagram of an embodiment of the voltage limit ellipse and the current limit circle;

[0025] Figure 2 It is a schematic diagram of another embodiment of the voltage limit ellipse and the current limit circle;

[0026] Figure 3 It is a schematic flowchart of an embodiment of the control method of the motor of the present invention;

[0027] Figure 4 It is a schematic flowchart of an embodiment of performing field weakening compensation on the d-axis and q-axis currents of the motor in the method of the present invention, and performing out-of-control limiting and compensation on the d-axis field weakening current of the motor;

[0028] Figure 5 It is a schematic flowchart of an embodiment of obtaining the dq-axis voltage according to the dq-axis current after field weakening in the method of the present invention;

[0029] Figure 6 It is a schematic flowchart of an embodiment of obtaining the d-axis current according to the q-axis current reference value of the motor in the method of the present invention;

[0030] Figure 7 It is a schematic flowchart of an embodiment of clamping the field weakening current at a set characteristic current after limiting in the method of the present invention;

[0031] Figure 8 It is a schematic flowchart of an embodiment of reducing the field weakening current to a set minimum value and performing reverse compensation on the q-axis current in the method of the present invention;

[0032] Figure 9 It is a schematic flowchart of an embodiment applied to the single q-axis current regulator control method;

[0033] Figure 10 It is a schematic control flowchart of an embodiment of a control method for a permanent magnet synchronous motor. Detailed Embodiments

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0035] Permanent magnet synchronous motors often need to operate within a wide speed regulation range in actual industrial applications. When operating below the base speed, the maximum torque per ampere (MTPA) control method is usually adopted, and when above the base speed, the field weakening control method is usually adopted. Field weakening speed increase control is a basic control method, and there are various field weakening control methods for different working conditions and different performance requirements. The wide range operation of permanent magnet synchronous motors mainly includes two operating regions. When the actual speed of the permanent magnet synchronous motor is less than the base speed, it is in the constant torque region, and the method adopted in the relevant scheme is the maximum torque per ampere (MTPA) control method; when the actual speed of the permanent magnet synchronous motor exceeds the base speed, at this time the permanent magnet synchronous motor control system is in the constant power region, that is, the field weakening control method needs to be adopted. Since the field weakening control method in the relevant scheme adopts double closed-loop vector control, two current PI regulators (i.e., proportional-integral regulators) are required to control the d-axis current i d and the q-axis current i q , respectively. However, there is parameter coupling between the two current PI regulators, and the probability of PI regulator saturation will increase, making parameter tuning more difficult. Therefore, based on this direction, the solution of the present invention is based on the single current loop control method for technical improvement.

[0036] In some single current regulator control methods of the schemes, when the given current is large and in the deep field weakening region, if the current trajectory planning is unreasonable, it is very easy to cause the actual current not to follow the given current, resulting in the rapid saturation of the current regulator, leading to current out of control, and in severe cases, it will also cause the instability of the permanent magnet synchronous motor system.

[0037] In addition, in some schemes, in the single d-axis current regulator control mode, although according to the voltage vector angle control method, the single d-axis current regulator control method can also be used for traction and braking control under field weakening conditions, but since the adjustment directions of the regulator in the two conditions are different and need to be designed separately, it will increase the complexity of the system.

[0038] Figure 1 It is a schematic diagram of an embodiment of the voltage limit ellipse and the current limit circle. Figure 2 It is a schematic diagram of another embodiment of the voltage limit ellipse and the current limit circle, that is, a schematic diagram of the voltage limit ellipse and the current limit circle when the permanent magnet synchronous motor system enters the deep field weakening region as the speed of the permanent magnet synchronous motor increases.

[0039] In the field weakening control method of the relevant scheme, Figure 1 It is a schematic diagram of the voltage limit ellipse and the current limit circle, where the amplitude of the current limit circle is a constant value, that is, I max , and the radius of the voltage limit ellipse decreases continuously as the motor speed increases. Figure 1The OA curve shown in the figure is the MTPA control process, and the ABC curve is the field-weakening control process. Then the O→A→B→C trajectory is the desired ideal current trajectory in motor control. Point C is the center of the voltage limit ellipse, and the current value here is the characteristic current value I of the motor. c . However, in actual control, due to different parameters of the actual motor control system, the relationship between the voltage limit ellipse and the current limit circle is also different. Moreover, as the speed further increases, the radius of the voltage limit ellipse further decreases, and the permanent magnet synchronous motor system enters the deep field-weakening region, specifically as Figure 2 shown.

[0040] Figure 2 Shown is the schematic diagram of the voltage limit ellipse and the current limit circle when the permanent magnet synchronous motor system enters the deep field-weakening region as the speed of the permanent magnet synchronous motor increases. When the speed of the permanent magnet synchronous motor rises to the point where the voltage limit ellipse and the current limit circle are only tangent at point A, at this time, the d-axis voltage u d = 0, and the q-axis voltage u q = -u max , and u max is the maximum value of the stator voltage. The controller is in a critical saturation state. When the speed of the permanent magnet synchronous motor continues to increase, the voltage limit ellipse further shrinks. At this time, there is no intersection between the current limit circle and the voltage limit ellipse. At this time, point A is always on the left side of the voltage limit ellipse, that is, the d-axis current reference value i d * is always less than the actual current i d , and at this time, the system will negatively regulate u d , and u d starts to decrease from 0. Since i d * is always less than i d , so u d will keep decreasing until u d is negatively saturated. At this time, u d = -u max , and the voltage angle is 5π / 4, as shown in Figure 2 . The motor stabilizes at point B, the intersection of the saturation out-of-control line and the voltage limit ellipse. During this process, i q * is always equal to 0. Therefore, u q is always equal to -u max . Since u d and u q are both in the saturation state, that is, the out-of-control state, but i d * is always increasing negatively. Therefore, the current command will always remain unchanged at point A.

[0041] Therefore, the current command always stays at point A, while the motor actually operates at point B, and there is a stable difference between the two, which will cause instability in the permanent magnet synchronous motor system. In an actual permanent magnet synchronous motor system, once the voltage limit ellipse intersects with the current limit circle to the left of the characteristic current, the motor may run out of control when actually operating at this point, and when u q < 0, it will also cause instability in the permanent magnet synchronous motor system, and even a small perturbation will make the actual d-axis current i d and the given d-axis current i d * change in inconsistent directions, resulting in instability. Therefore, in an actual permanent magnet synchronous motor system, the above situations should be avoided.

[0042] According to an embodiment of the present invention, a control method for a motor is provided, as shown in Figure 3 the schematic flow chart of an embodiment of the method of the present invention. The control method for the motor may include: step S110 to step S130.

[0043] At step S110, in the field weakening control system of the motor, a single q-axis current regulator is adopted to freely switch between field weakening traction and braking control under field weakening conditions.

[0044] At step S120, in the control system of the single q-axis current regulator, a field weakening compensation module is added to perform field weakening compensation processing on the d-axis and q-axis currents of the motor; and an out-of-control limiting and compensation module is added to perform out-of-control limiting and compensation processing on the d-axis field weakening current of the motor to obtain the voltage vector angle of the field weakening control system of the motor.

[0045] In some embodiments, in step S120, in the control system of the single q-axis current regulator, a field weakening compensation module is added to perform field weakening compensation processing on the d-axis and q-axis currents of the motor; and an out-of-control limiting and compensation module is added to perform out-of-control limiting and compensation processing on the d-axis field weakening current of the motor. For the specific process, refer to the following exemplary description.

[0046] The following combines Figure 4 the schematic flow chart of an embodiment of the method of the present invention for performing field weakening compensation processing on the d-axis and q-axis currents of the motor and performing out-of-control limiting and compensation processing on the d-axis field weakening current of the motor to further illustrate the specific process of performing field weakening compensation processing on the d-axis and q-axis currents of the motor and performing out-of-control limiting and compensation processing on the d-axis field weakening current of the motor in step S120, including: step S210 to step S240.

[0047] Step S210: In the field-weakening compensation module, the dq-axis voltages are obtained based on the dq-axis currents after field weakening. Then, the reference voltage amplitude is synthesized from the dq-axis voltages. After comparing and performing PI processing on the reference voltage amplitude with the maximum value of the stator voltage of the motor, the field-weakening compensation current is obtained.

[0048] In some embodiments, with reference to Figure 5 the schematic flowchart of an embodiment of obtaining the dq-axis voltages based on the dq-axis currents after field weakening in the method of the present invention as shown, the specific process of obtaining the dq-axis voltages based on the dq-axis currents after field weakening in step S210 is further described, including: step S310 to step S330.

[0049] Step S310: Obtain the basic parameters of the motor. The basic parameters include at least one of three-phase current, rotor position, and rotational speed.

[0050] Step S320: Based on the basic parameters of the motor, through coordinate transformation, the dq-axis currents in the dq-axis system are obtained as the dq-axis currents after field weakening.

[0051] Step S330: Based on the dq-axis currents after field weakening, through feedforward calculation, the dq-axis voltages are obtained. Among them, the dq-axis currents after field weakening are the field-weakening currents after being limited by the out-of-control limiting and compensation module.

[0052] As Figure 9 shown, the field-weakening compensation module is a general compensation method. However, different from other field-weakening compensation methods, the signal used for feedforward calculation here, that is, the dq-axis currents, are the field-weakening currents i d * _fw_lim and i q * _fw after being limited. Selecting the currents here is to establish the signal circulation between the field-weakening compensation module and the out-of-control limiting and compensation module to complete the signal closed-loop. Furthermore, synthesizing the stator voltage from the field-weakening currents to perform field weakening compensation on the d-axis current can achieve the purpose of more real-time control effect.

[0053] Step S220: Obtain the d-axis current based on the q-axis current reference value of the motor, and use the field-weakening compensation current to compensate the d-axis current to obtain the field-weakening current.

[0054] In some embodiments, with reference to Figure 6 the schematic flowchart of an embodiment of obtaining the d-axis current based on the q-axis current reference value of the motor in the method of the present invention as shown, the specific process of obtaining the d-axis current based on the q-axis current reference value of the motor in step S220 is further described, including: step S410 and step S420.

[0055] Step S410: In the outer speed loop of the motor, after comparing the actual speed of the motor with the reference speed and performing PI processing, the q-axis current reference value of the motor is obtained.

[0056] Step S420: Subject the q-axis current reference value of the motor to MTPA processing to obtain the d-axis current of the motor.

[0057] Figure 10 It is a schematic diagram of the control flow of an embodiment of a control method for a permanent magnet synchronous motor. As Figure 10 shown, a control method for a permanent magnet synchronous motor includes:

[0058] Step 1: Collect basic information such as three-phase current, rotor position, and speed, and obtain the currents i d and i q in the rotating coordinate dq-axis system through coordinate transformation. Specifically, collect three-phase current and rotor position information, and obtain the speed and dq-axis currents i d and i q , and then execute Step 2.

[0059] Step 2: In the outer speed loop, after comparing the actual speed of the motor with the reference speed and passing through a PI controller, the q-axis reference current i q * is obtained. That is, in the speed loop, after passing the given speed and the actual speed through a PI controller, the q-axis reference current i q * is obtained, and then execute Step 3.

[0060] Step 3: The q-axis reference current i q * passes through the MTPA module to obtain the d-axis current i d * _mtpa . That is, the q-axis reference current i q * , and the d-axis current i d * _mtpa is obtained through the MTPA (maximum torque per ampere control) control method, and then execute Step 4.

[0061] Among them, the d-axis current calculated from the q-axis current according to the MTPA formula, and the MTPA formula is:

[0062]

[0063] In the formula, ψ f is the permanent magnet flux linkage, i q * is the q-axis current reference value, Ld and L q is the dq-axis inductance.

[0064] Step 4. The d-axis current i d * _mtpa After being compensated by the field-weakening compensation current Δi d * _fw the field-weakening current i d * _fw is obtained. That is, the d-axis current i d * _mtpa , after being compensated by the d-axis field-weakening compensation current Δi d * _fw the field-weakening current i d * _fw is obtained, and then Step 5 can be executed.

[0065] Step S230. Based on the field-weakening current, enter the out-of-control limiting and compensation module. In the out-of-control limiting and compensation module, the field-weakening current is clamped at a set characteristic current after being limited.

[0066] In some embodiments, with reference to Figure 7 the schematic flowchart of an embodiment in the method of the present invention shown below for clamping the field-weakening current at a set characteristic current after being limited, the specific process of clamping the field-weakening current at a set characteristic current in Step S230 is further described, including: Step S510 and Step S520.

[0067] Step S510. The field-weakening current is the d-axis field-weakening current. After the d-axis field-weakening current is limited by the set characteristic current, the limited d-axis field-weakening current is obtained.

[0068] Step S520. The limited d-axis field-weakening current is restricted by the torque formula and the current limit circle to obtain the q-axis current value after field weakening.

[0069] As Figure 10 shown, a control method for a permanent magnet synchronous motor further includes:

[0070] After Step 4, Step 5. The field-weakening current i d * _fw , after being limited by the characteristic current I c the limited field-weakening current i d * _fw_lim, then at least one of Step 6, Step 7, and Step 8 is executed.

[0071] Specifically, the field-weakening current i d * _fw needs to be limited. After being limited by the characteristic current I c the limited field-weakening current i is obtained. d * _fw_lim . It should be noted that for a specific motor, the value of the characteristic current I c is a fixed parameter and can be actually measured.

[0072] Step 6, the limited field-weakening current i d * _fw_lim , according to the torque formula and the current limit circle constraint, the q-axis current value i after field weakening can be obtained. q * _fw , then at least one of Step 8 and Step 9 is executed.

[0073] Specifically, according to the torque expression and the constraint of the current limit circle, from the field-weakening current i d * _fw the q-axis field-weakening current i can be obtained. q * _fw The torque expression and the current limit circle expression are shown in Equations (1) and (2):

[0074] T e = 1.5N p [ψ f +(L d -L q )i d * _fw i q * _fw (1).

[0075] i d * _fw 2 +i q * _fw 2 = I max 2 (2).

[0076] Among them, T e is the torque of the permanent magnet synchronous motor, i q *_fw is the q-axis current value after field weakening, i d * _fw is the d-axis current value after field weakening, N p is the number of pole pairs of the motor, ψ f is the permanent magnet flux linkage, L d 、L q are the dq-axis inductances, I max is the radius of the current limit circle and also the maximum current value that the motor can withstand.

[0077] Step S240, as the speed of the motor increases, reduce the field weakening current to a set minimum value, perform reverse compensation on the q-axis current, and continue field weakening.

[0078] Figure 9 is a schematic flowchart of an embodiment applied to a single q-axis current regulator control method. The solution of the present invention proposes a single q-axis current regulator control method, and the specific control process is as Figure 9 shown. It can be seen from Figure 9 that the field weakening control structure is a single-loop control structure. In the field weakening compensation module, the dq-axis voltages are obtained by feedforward calculation from the dq-axis currents after field weakening, and then the reference voltage amplitude u s * fw is synthesized. After comparing with the maximum stator voltage u max , the field weakening compensation current Δi d * _fw is obtained through a PI controller. The q-axis current reference value i q * is used to obtain the d-axis current i d * _mtpa through MTPA operation. After compensation by the field weakening compensation current Δi d * _fw , the field weakening current i d * _fw can be obtained, and then it enters the out-of-control limiting and compensation module.

[0079] The solution of the present invention uses a method of limiting the d-axis current with the characteristic current I c to make the current command of the permanent magnet synchronous motor system always on the right side of the characteristic current point throughout the process, that is, to ensure that the permanent magnet synchronous motor system will not show unstable conditions. The characteristic current I c is an inherent parameter of the permanent magnet synchronous motor system and can be obtained through various methods, which will not be elaborated here. The field weakening current i d * _fwAfter being limited, it is clamped at the characteristic current I c , and is denoted as i at this time d * _fw_lim , when with the increase of the rotational speed, the field-weakening current decreases to its minimum value i d * _fw_lim , at this time the d-axis current cannot change any more, the q-axis current can be reversely compensated to continue field weakening, as shown in Figure 9 , the field-weakening current i d * _fw is subtracted from the field-weakening current i after limiting d * _fw_lim to obtain the compensation value Δi of the q-axis q , since the d-axis current in the field-weakening control is all negative, the compensation value Δi of the q-axis q is also negative, that is, further field-weakening control is achieved by reducing the q-axis current value. According to the torque formula and the current limit circle restriction, from the field-weakening current i d * _fw the q-axis current i q * _fw can be obtained. After the q-axis current is compensated and compared with the actual q-axis current i q , through the PI controller, the voltage vector angle θ u can be obtained. In the field-weakening control system, the only variable that can be controlled is the voltage vector angle θ u . From the relationship between the voltage vector angle θ u and the maximum stator voltage u max , the reference voltage vectors u d * and u q * of the dq axes can be obtained, and then through the SVPWM (Space Vector Pulse Width Modulation) module, the PWM wave can be generated to achieve the drive control of the motor system.

[0080] In some embodiments, in step S240, with the increase of the rotational speed of the motor, the field-weakening current is reduced to the set minimum value, and the specific process of reversely compensating the q-axis current and continuing field weakening is as follows in the exemplary description.

[0081] The following is combined with Figure 8A schematic flowchart of an embodiment of reducing the field-weakening current to a set minimum value and performing reverse compensation on the q-axis current in the method of the present invention, further illustrating the specific process of reducing the field-weakening current to the set minimum value and performing reverse compensation on the q-axis current in step S240, including: steps S610 to S630.

[0082] Step S610: Determine the difference between the d-axis field-weakening current before limiting and the d-axis field-weakening current after limiting, denoted as the first difference. Use the first difference to compensate the d-axis field-weakening current after limiting and continue field weakening. And,

[0083] Step S620: Add the first difference to the q-axis current value after field weakening, compare it with the actual q-axis current of the motor and perform PI processing to obtain the voltage vector angle of the motor.

[0084] Step S630: Determine the d-axis field-weakening current after limiting and the q-axis current value after field weakening. Use the d-axis field-weakening current after limiting and the q-axis current value after field weakening for feedforward calculation to obtain the actual value of the stator voltage of the motor, so as to determine the dq-axis reference voltage vector of the motor according to the voltage vector angle and the maximum value of the stator voltage of the motor.

[0085] At step S130, determine the dq-axis reference voltage vector of the motor according to the voltage vector angle and the maximum value of the stator voltage of the motor, so as to perform drive control on the system where the motor is located according to the dq-axis reference voltage vector.

[0086] The motor control system needs field weakening to increase speed to broaden its speed regulation range, so a field weakening control method needs to be adopted. In the field weakening control of related solutions, there is a risk of cross-coupling and saturation between the two current regulators. Therefore, the solution of the present invention uses a single current regulator control method as the basic framework.

[0087] The field-weakening control of related solutions usually adopts a dual-current-loop control method. However, there is mutual coupling between the parameters of the two current regulators, that is, when adjusting the parameters of one PI regulator, the performance of the other current also changes accordingly, that is, they affect each other, and there is even a possibility of saturation of the PI regulator, that is, the output capacity of the PI regulator reaches the upper limit. At this time, adjusting the PI parameters can no longer control the current performance, that is, the current gets out of control, and this situation is not allowed. Therefore, the solution of the present invention adopts a single-current-loop control method. Compared with the dual-loop, the influence of parameter coupling under single-loop control is reduced, and only a set of PI parameters needs to be adjusted. In addition, the risk of saturation of the PI regulator is also reduced because, without considering parameter coupling, the adjustment of PI parameters will be easier, and it is always easier to debug a set of PI parameters than two sets of PI parameters. Therefore, it can be said that the single-loop control method can avoid the instability of the permanent magnet synchronous motor control system caused by cross-coupling between controllers.

[0088] Thus, the solution of the present invention proposes a field-weakening control method for a permanent magnet synchronous motor based on a single q-axis current regulator control method. Its current control module only adopts a single q-axis current regulator, avoiding the difficulties in parameter tuning, easy saturation of the controller, and cross-coupling phenomenon caused by dual-loop control. A field-weakening out-of-control suppression method is adopted in the single-current-loop control structure. By limiting the field-weakening current and compensating the q-axis current, field-weakening out-of-control is avoided and deep field-weakening of the permanent magnet synchronous motor system is achieved.

[0089] The solution of the present invention adopts a field-weakening control method with a single q-axis current regulator, which can freely switch between field-weakening traction and braking control. That is to say, a field-weakening out-of-control suppression and compensation method based on a single q-axis current regulator is adopted. By using a single q-axis current regulator, free switching between traction and braking control can be carried out under field-weakening conditions, and the instability of the permanent magnet synchronous motor system caused by the cross-coupling phenomenon between controllers (i.e., dual current regulators) brought about by the dual-loop structure can be avoided.

[0090] Field-weakening traction means that under field-weakening control, the traction of the motor is realized. Intuitively, the electromagnetic torque drives the motor to rotate. At this time, the torque is a positive torque, T e > 0, corresponding to the torque current i q > 0; in the braking condition, the braking of the motor is realized. Intuitively, the electromagnetic torque hinders the rotation of the motor. At this time, the torque is a negative torque, T e < 0, corresponding to the torque current i q < 0; freely switching between field-weakening traction and braking control, this characteristic is determined by the characteristics of the single q-axis current regulator. The basic framework of the present invention adopts a single q-axis current regulator control method, so it can freely switch between traction and braking.

[0091] Problems existing in the single current regulator of some solutions. In the deep field-weakening region, if no amplitude limiting control is applied, there is also a possibility of current runaway. The problem of the selection of the single current regulator control in some solutions. The single current loop control is divided into single d-axis current regulator control and single q-axis current regulator control. Compared with the single d-axis current regulator control.

[0092] Considering that in the single current loop control, when entering the deep field-weakening region, there is also a possibility of current runaway. Therefore, the solution of the present invention adopts a control method combining an amplitude limiting method and a current compensation method.

[0093] Specifically, the single q-axis current regulator control method selected in the solution of the present invention can smoothly switch between the traction and braking modes during the operation of the motor, which is determined by the working characteristics of the single q-axis current regulator. The method proposed in the solution of the present invention adds a field-weakening current amplitude limiting module and a current compensation module to the single q-axis current regulator control system, avoiding field-weakening runaway and instability of the permanent magnet synchronous motor system caused by the non-following of the current in the deep field-weakening region. That is to say, by adopting the single q-axis current regulator, free switching between traction and braking control can be performed under the field-weakening working condition, and at the same time, a current amplitude limiting method is adopted to avoid the phenomenon that the actual current does not follow the given current due to unreasonable current trajectory planning in the deep field-weakening region.

[0094] Correspondingly, in step S130, determining the dq-axis reference voltage vector of the motor according to the voltage vector angle and the maximum stator voltage of the motor includes: combining the voltage vector angle of the motor with the maximum stator voltage of the motor, and after voltage amplitude operation, obtaining the dq-axis reference voltage of the motor to obtain the voltage vector angle of the field-weakening control system of the motor.

[0095] As Figure 10 shown, a control method for a permanent magnet synchronous motor further includes:

[0096] After step 4, step 7: In the d-axis field-weakening current amplitude limiting module, the field-weakening current value i d * _fw before amplitude limiting and the field-weakening current i d * _fw_lim after amplitude limiting are subtracted to obtain a difference value Δi q , and the field-weakening current value i q * _fw after amplitude limiting is compensated, and then step 9 is executed.

[0097] Specifically, in step 7, the difference value Δi qCompensate the q-axis field-weakening current. When the d-axis current reaches its limit value, the method of reducing the d-axis current can no longer be used to increase the speed. At this time, the q-axis current can be compensated to achieve further field weakening and continue to increase the speed.

[0098] Step 8. The field-weakening current i after limiting d * _fw_lim and the q-axis current value i after field weakening q * _fw , and the actual stator voltage value u is obtained through feed-forward calculation s * fw , and then step 11 is executed.

[0099] Specifically, in step 8, after obtaining the field-weakening current i after limiting d * _fw_lim and the q-axis current value i after field weakening q * _fw , the actual stator voltage value u can be obtained according to the feed-forward calculation formula s * _fw . The feed-forward calculation formula is shown in Equation (3):

[0100]

[0101] In the formula, ω s is the actual motor speed, and then the actual stator voltage value u can be obtained from Equation (4) s * _fw :

[0102]

[0103] Among them, ψ f is the permanent magnet flux linkage, L d , L q are the dq-axis inductances, u d * _fw is the d-axis component of the stator voltage, u q * _fw is the q-axis component of the stator voltage, and the rest of the symbols are all marked.

[0104] Step 9. Add the difference Δi q to the q-axis field-weakening current i q * _fw and add it to the actual q-axis current i qAfter comparison, the voltage vector angle θ is obtained through a PI controller u , in the field-weakening control, the only controlled variable is the voltage vector angle θ u . That is, the field-weakening current value i d * _fw after amplitude limiting and the field-weakening current i d * _fw_lim after amplitude limiting, the difference Δi q , is added to the field-weakening current value i q * _fw after amplitude limiting, and after comparison with the actual q-axis current i q , the voltage vector angle θ is generated through a PI module u , and then step 10 is executed.

[0105] Step 10: From the voltage vector angle θ u combined with the maximum stator voltage u max , after voltage amplitude operation, the dq-axis reference voltages u d * and u q * u are obtained, and then through the SVPWM module, PWM waves can be generated to achieve the drive control of the permanent magnet synchronous motor system.

[0106] Specifically, in step 10, from the voltage vector angle θ u , after operation with the voltage limit value u max , the dq-axis reference voltages u d * and u q * s are obtained, as shown in formula (5), and then through the SVPWM module, PWM waves can be generated to achieve the drive control of the motor system:

[0107]

[0108] Step 11: After comparison between the actual stator voltage u s * fw and the maximum stator voltage u max , the d-axis field-weakening current compensation value Δi d * _fw is obtained, and the d-axis current i d * _mtpa s is compensated. That is, after the actual stator voltage u s * fw and the voltage limit value pass through a PI module, the field-weakening compensation current Δi is obtainedd * _fw , then return to step 4. That is, from the actual value of the stator voltage u s * _fw Compared with the voltage limit value u max After passing through a PI controller, the field-weakening compensation current Δi is obtained d * _fw Compensate the d-axis current i in step 4 d * _mtpa .

[0109] In the solution of the present invention, an out-of-control limit and compensation module is provided in the single q-axis current loop. First, in the control method of the single q-axis current regulator, the solution of the present invention adds a limit module for the d-axis field-weakening current, and takes the difference between the values before and after the limit, and the difference value is used as the field-weakening compensation amount of the q-axis current to perform field-weakening on the q-axis current, that is, as in Figure 9 As shown in the example, the permanent magnet synchronous motor system performs two-step field-weakening. The first step is the field-weakening and limiting of the d-axis current, and then the second step of field-weakening is performed, that is, the field-weakening of the q-axis current. After the out-of-control limit and compensation module finishes working, it enters the PI regulator to output the control signal, and the output quantity is the voltage vector angle θ u , which is the only controlled quantity in the field-weakening control. The above is the so-called single q-axis current regulator control.

[0110] After a large number of experimental verifications, by adopting the technical solution of this embodiment, in the field-weakening control method of the permanent magnet synchronous motor, by adopting a single q-axis current regulator, it is possible to freely switch between traction and braking control under field-weakening conditions, and add a field-weakening current limit module and a current compensation module in the control system of the single q-axis current regulator for limiting and current compensation. By adopting a single current loop control structure in the field-weakening control of the permanent magnet synchronous motor and adopting a limiting method and a current compensation method for field-weakening control, it is possible to avoid the instability of the permanent magnet synchronous motor control system and is beneficial to improving the reliability of the field-weakening control of the permanent magnet synchronous motor.

[0111] According to an embodiment of the present invention, there is also provided a control device for an electric motor corresponding to the control method of the electric motor. The control device for the electric motor may include: a control unit.

[0112] Wherein, the control unit is configured to adopt a single q-axis current regulator in the field-weakening control system of the electric motor, and freely switch between field-weakening traction and braking control under field-weakening conditions. For the specific functions and processes of the control unit, refer to step S110.

[0113] The control unit is further configured to add a field weakening compensation module to the control system of the single q-axis current regulator to perform field weakening compensation processing on the d-axis and q-axis currents of the motor; and add an out-of-control limiting and compensation module to perform out-of-control limiting and compensation processing on the d-axis field weakening current of the motor to obtain the voltage vector angle of the field weakening control system of the motor. For the specific functions and processing of this control unit, refer to step S120

[0114] In some embodiments, the control unit adds a field weakening compensation module to the control system of the single q-axis current regulator to perform field weakening compensation processing on the d-axis and q-axis currents of the motor; and adds an out-of-control limiting and compensation module to perform out-of-control limiting and compensation processing on the d-axis field weakening current of the motor, including:

[0115] The control unit is specifically further configured to obtain dq-axis voltages from the dq-axis currents after field weakening in the field weakening compensation module, and then synthesize the dq-axis voltages into a reference voltage amplitude, and then compare the reference voltage amplitude with the maximum value of the stator voltage of the motor and perform PI processing to obtain the field weakening compensation current. For the specific functions and processing of this control unit, refer to step S210

[0116] In some embodiments, the control unit obtaining dq-axis voltages from the dq-axis currents after field weakening includes:

[0117] The control unit is specifically further configured to obtain the basic parameters of the motor. The basic parameters include at least one of three-phase current, rotor position, and speed. For the specific functions and processing of this control unit, refer to step S310

[0118] The control unit is specifically further configured to obtain the dq-axis currents in the dq-axis system through coordinate transformation according to the basic parameters of the motor as the dq-axis currents after field weakening. For the specific functions and processing of this control unit, refer to step S320

[0119] The control unit is specifically further configured to obtain dq-axis voltages through feedforward calculation according to the dq-axis currents after field weakening. The dq-axis currents after field weakening are the field weakening currents after being limited by the out-of-control limiting and compensation module. For the specific functions and processing of this control unit, refer to step S330

[0120] As Figure 9 shown, the field weakening compensation module is a general compensation method, but different from other field weakening compensation methods, the signals used for feedforward calculation here, that is, the dq-axis currents, are the field weakening currents i d * _fw_lim and i q* _fw The current selected here is to establish the signal circulation between the field-weakening compensation module and the out-of-control limiting and compensation module to complete the signal closed-loop. Furthermore, the stator voltage is synthesized from the field-weakening current to perform field-weakening compensation on the d-axis current, achieving a more real-time control effect.

[0121] The control unit is specifically further configured to obtain the d-axis current according to the q-axis current reference value of the motor, and compensate the d-axis current with the field-weakening compensation current to obtain the field-weakening current. For the specific functions and processes of this control unit, please also refer to step S220.

[0122] In some embodiments, the control unit obtaining the d-axis current according to the q-axis current reference value of the motor includes:

[0123] The control unit is specifically further configured to compare the actual speed of the motor with the reference speed and perform PI processing in the outer speed loop of the motor to obtain the q-axis current reference value of the motor. For the specific functions and processes of this control unit, please also refer to step S410.

[0124] The control unit is specifically further configured to subject the q-axis current reference value of the motor to MTPA processing to obtain the d-axis current of the motor. For the specific functions and processes of this control unit, please also refer to step S420.

[0125] Figure 10 It is a schematic diagram of the control flow of an embodiment of a control device for a permanent magnet synchronous motor. As Figure 10 shown, a control device for a permanent magnet synchronous motor includes:

[0126] Step 1: Collect basic information such as three-phase current, rotor position, and speed, and obtain the currents i d 、i q in the rotating coordinate dq axis system through coordinate transformation. Specifically, collect the three-phase current and rotor position information, and obtain the speed and dq axis currents i d 、i q , and then execute step 2.

[0127] Step 2: In the outer speed loop, compare the actual speed of the motor with the reference speed and then pass through a PI controller to obtain the q-axis reference current i q * . That is, in the speed loop, the q-axis reference current i q * is obtained after passing through the PI controller from the given speed and the actual speed, and then execute step 3.

[0128] Step 3: The q-axis reference current i q *The d-axis current i is obtained through the MTPA module d * _mtpa That is, the q-axis reference current i q * and the d-axis current i is obtained through the MTPA (Maximum Torque per Ampere control) control device d * _mtpa Then, step 4 is executed

[0129] Step 4: The d-axis current i d * _mtpa After being compensated by the field-weakening compensation current Δi d * _fw the field-weakening current i is obtained d * _fw That is, the d-axis current i d * _mtpa after being compensated by the d-axis field-weakening compensation current Δi d * _fw the field-weakening current i is obtained d * _fw Then, step 5 can be executed

[0130] The control unit is specifically further configured to enter the out-of-control limiting and compensation module based on the field-weakening current. In the out-of-control limiting and compensation module, the field-weakening current is clamped at a set characteristic current after being limited. For the specific functions and processing of this control unit, refer to step S230

[0131] In some embodiments, the control unit clamping the field-weakening current at a set characteristic current after being limited includes:

[0132] The control unit is specifically further configured that the field-weakening current is the d-axis field-weakening current. After the d-axis field-weakening current is limited by the set characteristic current, the limited d-axis field-weakening current is obtained. For the specific functions and processing of this control unit, refer to step S510

[0133] The control unit is specifically further configured to obtain the q-axis current value after field-weakening by limiting the limited d-axis field-weakening current through the torque formula and the current limit circle. For the specific functions and processing of this control unit, refer to step S520

[0134] As Figure 10 shown in, a control device for a permanent magnet synchronous motor further includes:

[0135] After step 4, in step 5, the field-weakening current i d * _fw , through the characteristic current I c limiting, the limited field-weakening current i d * _fw_lim is obtained, and then at least one of step 6, step 7, and step 8 is executed.

[0136] Specifically, the field-weakening current i d * _fw needs to be limited. Through the characteristic current I c limiting, the limited field-weakening current i d * _fw_lim is obtained. It should be noted that for a specific motor, the value of the characteristic current I c is a fixed parameter and can be actually measured.

[0137] Step 6, the limited field-weakening current i d * _fw_lim , according to the torque formula and the current limit circle constraint, the q-axis current value i q * _fw after field weakening can be obtained, and then at least one of step 8 and step 9 is executed.

[0138] Specifically, according to the torque expression and the current limit circle constraint, from the field-weakening current i d * _fw the q-axis field-weakening current i q * _fw can be obtained. The torque expression and the current limit circle expression are shown in equations (1) and (2):

[0139] T e = 1.5N p [ψ f +(L d -L q )i d * _fw i q * _fw (1).

[0140] i d * _fw 2 +i q * _fw2 = I max 2 (2).

[0141] Wherein, T e is the torque of the permanent magnet synchronous motor, and i q * _fw is the q-axis current value after field weakening, and i d * _fw is the d-axis current value after field weakening.

[0142] The control unit is specifically further configured to reduce the field weakening current to a set minimum value as the speed of the motor increases, perform reverse compensation on the q-axis current, and continue field weakening. For the specific functions and processes of this control unit, refer to step S240.

[0143] Figure 9 is a schematic flowchart of an embodiment applied to a single q-axis current regulator control device. The solution of the present invention proposes a single q-axis current regulator control device, and the specific control process is as Figure 9 shown. It can be seen from Figure 9 that this field weakening control structure is a single-loop control structure. In the field weakening compensation module, the dq-axis voltages are obtained through feedforward calculation from the dq-axis currents after field weakening, and then the reference voltage amplitude u s * fw is synthesized. After comparison with the maximum stator voltage u max , the field weakening compensation current Δi d * _fw is obtained through a PI controller. The q-axis current reference value i q * is used to obtain the d-axis current i d * _mtpa through MTPA operation. After compensation by the field weakening compensation current Δi d * _fw , the field weakening current i d * _fw can be obtained, and at this time, it enters the out-of-control limiting and compensation module.

[0144] The solution of the present invention adopts a device that limits the d-axis current with the characteristic current I c to make the current command of the permanent magnet synchronous motor system always be on the right side of the characteristic current point throughout the process, that is, to ensure that the permanent magnet synchronous motor system will not exhibit unstable conditions. The characteristic current I cis an inherent parameter of the permanent magnet synchronous motor system and can be obtained through various devices, which will not be elaborated here. The field-weakening current i d * _fw is clamped at the characteristic current I c after amplitude limiting, and is denoted as i d * _fw_lim at this time. When the speed increases, the field-weakening current decreases to its minimum value i d * _fw_lim . At this time, the d-axis current cannot change anymore, and the q-axis current can be reversely compensated to continue field weakening. As shown in Figure 9 , the difference between the field-weakening current i d * _fw and the amplitude-limited field-weakening current i d * _fw_lim is taken to obtain the compensation value Δi q of the q-axis. Since the d-axis current in the field-weakening control is negative, the compensation value Δi q of the q-axis is also negative, that is, further field-weakening control is achieved by reducing the q-axis current value. According to the torque formula and the current limit circle restriction, the q-axis current i d * _fw can be obtained from the field-weakening current i q * _fw . After the q-axis current is compensated and compared with the actual q-axis current i q , the voltage vector angle θ u can be obtained through a PI controller. In the field-weakening control system, the only variable that can be controlled is the voltage vector angle θ u . From the relationship between the voltage vector angle θ u and the maximum stator voltage u max , the dq-axis reference voltage vectors u d * and u q * can be obtained, and then a PWM wave can be generated through the SVPWM (Space Vector Pulse Width Modulation) module to achieve the drive control of the motor system.

[0145] In some embodiments, the control unit, as the speed of the motor increases, reduces the field-weakening current to a set minimum value, reversely compensates the q-axis current, and continues field weakening, including:

[0146] The control unit is further specifically configured to determine the difference between the d-axis field-weakening current before amplitude limiting and the d-axis field-weakening current after amplitude limiting, denoted as the first difference. The d-axis field-weakening current after amplitude limiting is compensated using the first difference to continue field weakening. For the specific functions and processing of this control unit, refer to step S610. Also,

[0147] The control unit is further specifically configured to add the first difference to the q-axis current value after field weakening, and after comparing with the actual q-axis current of the motor and performing PI processing, obtain the voltage vector angle of the motor. For the specific functions and processing of this control unit, refer to step S620.

[0148] The control unit is further specifically configured to determine the d-axis field-weakening current after amplitude limiting and the q-axis current value after field weakening. Feedforward calculation is performed using the d-axis field-weakening current after amplitude limiting and the q-axis current value after field weakening to obtain the actual value of the stator voltage of the motor, so as to determine the dq-axis reference voltage vector of the motor according to the voltage vector angle and the maximum value of the stator voltage of the motor. For the specific functions and processing of this control unit, refer to step S630.

[0149] The control unit is further configured to determine the dq-axis reference voltage vector of the motor according to the voltage vector angle and the maximum value of the stator voltage of the motor, so as to perform drive control on the system where the motor is located according to the dq-axis reference voltage vector. For the specific functions and processing of this control unit, refer to step S130.

[0150] The motor control system needs field weakening to increase speed to broaden its speed regulation range, so a field weakening control device needs to be adopted. In the field weakening control of related solutions, there is a risk of cross-coupling and saturation between the two current regulators. Therefore, the solution of the present invention uses a single current regulator control device as the basic framework.

[0151] The field weakening control of related solutions usually adopts a double current loop control device, and there is mutual coupling of parameters between the two current regulators, that is, when adjusting the parameters of one PI regulator, the performance of the other current also changes accordingly, that is, they affect each other, and there is even a possibility of saturation of the PI regulator, that is, the output ability of the PI regulator reaches the upper limit. At this time, adjusting the PI parameters can no longer control the current performance, that is, the current gets out of control, and this situation is not allowed. Therefore, the solution of the present invention adopts a single current loop control device. Compared with the double loop, the influence of parameter coupling is reduced under single loop control, and only a set of PI parameters need to be adjusted. In addition, the risk of saturation of the PI regulator is also reduced because without considering parameter coupling, the adjustment of PI parameters will be easier, and a set of PI parameters is always easier to debug than two sets of PI parameters. Therefore, it can be said that the single loop control device can avoid the instability of the permanent magnet synchronous motor control system caused by cross-coupling between controllers.

[0152] Thus, the solution of the present invention proposes a field-weakening control device for a permanent magnet synchronous motor based on a single q-axis current regulator control device. Its current control module only uses one single q-axis current regulator, avoiding the problems of difficult parameter tuning, easy saturation of the controller, and cross-coupling phenomenon caused by double-loop control. A field-weakening runaway suppression device is adopted in the single-current-loop control structure. By limiting the field-weakening current and compensating the q-axis current, field-weakening runaway is avoided and deep field-weakening of the permanent magnet synchronous motor system is achieved.

[0153] The solution of the present invention adopts a field-weakening control device with a single q-axis current regulator, which can freely switch between field-weakening traction and braking control. That is to say, a field-weakening runaway suppression and compensation device based on a single q-axis current regulator is adopted. By using a single q-axis current regulator, free switching between traction and braking control can be carried out under field-weakening conditions, and instability of the permanent magnet synchronous motor system caused by the cross-coupling phenomenon between controllers (i.e., double current regulators) brought by the double-loop structure can be avoided.

[0154] Regarding some problems existing in the single current regulator of some solutions, in the deep field-weakening region, if no amplitude limiting control is applied, there is also a possibility of current runaway. There are also issues regarding the selection of the single current regulator control in some solutions. Single-current-loop control is divided into single d-axis current regulator control and single q-axis current regulator control. Compared with single d-axis current regulator control.

[0155] Considering that in single-current-loop control, when entering the deep field-weakening region, there is also a possibility of current runaway. Therefore, the solution of the present invention adopts a control method combining an amplitude limiting method and a current compensation method.

[0156] Specifically, the single q-axis current regulator control device selected by the solution of the present invention can smoothly switch between the traction and braking modes during the operation of the motor, which is determined by the working characteristics of the single q-axis current regulator. The device proposed by the solution of the present invention adds a field-weakening current amplitude limiting module and a current compensation module to the single q-axis current regulator control system, avoiding field-weakening runaway and instability of the permanent magnet synchronous motor system caused by the non-following of current in the deep field-weakening region. That is to say, by using a single q-axis current regulator, free switching between traction and braking control can be carried out under field-weakening conditions, and at the same time, a current amplitude limiting device is adopted to avoid the phenomenon that the actual current does not follow the given current due to unreasonable current trajectory planning in the deep field-weakening region.

[0157] Correspondingly, the control unit determines the dq-axis reference voltage vectors of the motor according to the voltage vector angle and the maximum value of the stator voltage of the motor, including:

[0158] The control unit is specifically further configured to combine the voltage vector angle of the motor with the maximum value of the stator voltage of the motor, and after performing voltage amplitude calculation, obtain the dq-axis reference voltage of the motor, so as to obtain the voltage vector angle of the field-weakening control system of the motor.

[0159] As Figure 10 shown in, a control device for a permanent magnet synchronous motor further includes:

[0160] After step 4, step 7: In the d-axis field-weakening current limiting module, the field-weakening current value i before limiting d * _fw is subtracted from the field-weakening current i after limiting d * _fw_lim to obtain a difference value Δi q , and the field-weakening current value i after limiting q * _fw is compensated, and then step 9 is executed.

[0161] Specifically, in step 7, the difference value Δi between before and after the d-axis field-weakening current limiting q compensates the q-axis field-weakening current. When the d-axis current reaches its limiting value, the device for reducing the d-axis current can no longer be used to achieve speed increase. At this time, the q-axis current can be compensated to achieve a further field-weakening effect and continue to increase the speed.

[0162] Step 8: The field-weakening current i after limiting d * _fw_lim and the q-axis current value i after field-weakening q * _fw are used to obtain the actual value u of the stator voltage through feedforward calculation s * fw , and then step 11 is executed.

[0163] Specifically, in step 8, after obtaining the field-weakening current i after limiting d * _fw_lim and the q-axis current value i after field-weakening q * _fw , the actual value u of the stator voltage can be obtained according to the feedforward calculation formula s * _fw , and the feedforward calculation formula is as shown in formula (3):

[0164]

[0165] In the formula, ωs is the actual rotational speed of the motor, and then the actual value u of the stator voltage can be further obtained from Equation (4). s * _fw :

[0166]

[0167] Step 9, the difference Δi q is added to the q-axis field-weakening current i q * _fw and compared with the actual q-axis current i q After comparison, the voltage vector angle θ is obtained through a PI controller u . In field-weakening control, the only controlled variable is the voltage vector angle θ u . That is, the field-weakening current value i d * _fw after amplitude limiting is added to the field-weakening current i d * _fw_lim after amplitude limiting, and the difference Δi q is added to the field-weakening current value i q * _fw after amplitude limiting and compared with the actual q-axis current i q . After passing through a PI module, the voltage vector angle θ is generated u , and then Step 10 is executed.

[0168] Step 10, from the voltage vector angle θ u combined with the maximum value u of the stator voltage max , after voltage amplitude calculation, the dq-axis reference voltages u d * and u q * are obtained, and then through the SVPWM module, PWM waves can be generated to achieve the drive control of the permanent magnet synchronous motor system.

[0169] Specifically, in Step 10, from the voltage vector angle θ u , after calculation with the voltage limit value u max , the dq-axis reference voltages u d * and u q * are obtained. The formula is shown in Equation (5). Then, through the SVPWM module, PWM waves can be generated to achieve the drive control of the motor system:

[0170]

[0171] Step 11, the actual value u of the stator voltages * fw After comparing with the maximum stator voltage u max the d-axis field-weakening current compensation value Δi is obtained d * _fw , and the d-axis current i d * _mtpa is compensated. That is, the actual stator voltage u s * fw and the voltage limit value pass through the PI module to obtain the field-weakening compensation current Δi d * _fw , and then return to step 4. That is to say, the actual stator voltage u s * _fw and the voltage limit value u max are compared and then pass through the PI controller to obtain the field-weakening compensation current Δi d * _fw to compensate the d-axis current i d * _mtpa in step 4.

[0172] In the solution of the present invention, a runaway limit and compensation module is provided in the single q-axis current loop. First, in the single q-axis current regulator control device, the present invention adds a limit module for the d-axis field-weakening current, and takes the difference between the values before and after limiting, and the difference is used as the field-weakening compensation amount of the q-axis current to perform field-weakening on the q-axis current, that is, as in Figure 9 the example shown, the permanent magnet synchronous motor system performs two-step field-weakening. The first step is the field-weakening and limiting of the d-axis current, and then the second step of field-weakening is performed, that is, the field-weakening of the q-axis current. After the runaway limit and compensation module finishes working, it enters the PI regulator to output the control signal, and the output quantity is the voltage vector angle θ u , which is the only controlled quantity in the field-weakening control. The above is the so-called single q-axis current regulator control.

[0173] Since the processing and functions implemented by the device in this embodiment are basically corresponding to the embodiments, principles and examples of the foregoing method, for the parts not described in detail in the description of this embodiment, reference may be made to the relevant descriptions in the foregoing embodiments, and details are not described herein again.

[0174] After a large number of experimental verifications, by adopting the technical solution of the present invention, in the field-weakening control method of a permanent magnet synchronous motor, a single q-axis current regulator is used, which can freely switch between traction and braking control under field-weakening conditions. Moreover, a field-weakening current limiting module and a current compensation module are added to the control system of the single q-axis current regulator for current limiting and compensation, which can avoid the instability of the permanent magnet synchronous motor system caused by the cross-coupling phenomenon between controllers (i.e., dual current regulators) brought by the double-loop structure.

[0175] According to an embodiment of the present invention, there is also provided a motor corresponding to the control device of the motor. The motor may include: the control device of the motor described above.

[0176] Since the processing and functions implemented by the motor in this embodiment are basically corresponding to the embodiments, principles, and examples of the foregoing device, for the details not described in the description of this embodiment, reference may be made to the relevant descriptions in the foregoing embodiments, and details will not be repeated here.

[0177] After a large number of experimental verifications, by adopting the technical solution of the present invention, in the field-weakening control method of a permanent magnet synchronous motor, a single q-axis current regulator is used, which can freely switch between traction and braking control under field-weakening conditions. Moreover, a field-weakening current limiting module and a current compensation module are added to the control system of the single q-axis current regulator for current limiting and compensation, avoiding field-weakening out-of-control and achieving deep field-weakening of the permanent magnet synchronous motor system.

[0178] According to an embodiment of the present invention, there is also provided a storage medium corresponding to the control method of the motor. The storage medium includes a stored program, wherein when the program runs, it controls the device where the storage medium is located to execute the control method of the motor described above.

[0179] Since the processing and functions implemented by the storage medium in this embodiment are basically corresponding to the embodiments, principles, and examples of the foregoing method, for the details not described in the description of this embodiment, reference may be made to the relevant descriptions in the foregoing embodiments, and details will not be repeated here.

[0180] After a large number of experimental verifications, by adopting the technical solution of the present invention, in the field-weakening control method of a permanent magnet synchronous motor, a single q-axis current regulator is used, which can freely switch between traction and braking control under field-weakening conditions. Moreover, a field-weakening current limiting module and a current compensation module are added to the control system of the single q-axis current regulator for current limiting and compensation, avoiding field-weakening out-of-control and instability of the permanent magnet synchronous motor system caused by the non-following of the current in the deep field-weakening region.

[0181] According to an embodiment of the present invention, there is also provided a processor corresponding to the control method of the motor. The processor is used to run a program, wherein when the program runs, it executes the control method of the motor described above.

[0182] Since the processing and functions implemented by the processor in this embodiment are basically corresponding to the embodiments, principles, and examples of the foregoing method, for the parts not described in detail in the description of this embodiment, reference may be made to the relevant descriptions in the foregoing embodiments and will not be elaborated herein.

[0183] After a large number of experimental verifications, by adopting the technical solution of the present invention, in the field-weakening control method of a permanent magnet synchronous motor, a single q-axis current regulator is adopted, so that the free switching between traction and braking control can be carried out under the field-weakening condition, and a field-weakening current limiting module and a current compensation module are added to the control system of the single q-axis current regulator for current limiting and current compensation, thereby avoiding the phenomenon that the actual current does not follow the given current due to unreasonable current trajectory planning in the deep field-weakening region.

[0184] In summary, it is easy for those skilled in the art to understand that, on the premise of no conflict, the above-mentioned advantageous ways can be freely combined and superimposed.

[0185] The above are only the embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A control method for an electric motor, characterized in that, it includes: In the field-weakening control system of the electric motor, a single q-axis current regulator is adopted to freely switch between field-weakening traction and braking control under field-weakening conditions; In the control system of the single q-axis current regulator, a field-weakening compensation module is added to perform field-weakening compensation processing on the d-axis and q-axis currents of the electric motor to obtain the d-axis field-weakening current; and an out-of-control limiting and compensation module is added to perform out-of-control limiting and compensation processing on the d-axis field-weakening current of the electric motor to obtain the voltage vector angle of the field-weakening control system of the electric motor; wherein, adding an out-of-control limiting and compensation module to perform out-of-control limiting and compensation processing on the d-axis field-weakening current of the electric motor includes: in the out-of-control limiting and compensation module, the d-axis field-weakening current is clamped at a set characteristic current after limiting to obtain the limited d-axis field-weakening current; as the speed of the electric motor increases, the limited d-axis field-weakening current is reduced to a set minimum value, and the q-axis current is reversely compensated to continue field-weakening; According to the voltage vector angle and the maximum stator voltage of the electric motor, determine the dq-axis reference voltage vector of the electric motor, so as to drive and control the system where the electric motor is located according to the dq-axis reference voltage vector.

2. The control method for an electric motor according to claim 1, characterized in that, In the control system of the single q-axis current regulator, adding a field-weakening compensation module to perform field-weakening compensation processing on the d-axis and q-axis currents of the electric motor to obtain the d-axis field-weakening current includes: In the field-weakening compensation module, the dq-axis voltage is obtained according to the q-axis field-weakening current and the limited d-axis field-weakening current, and then the dq-axis voltage is synthesized into the reference voltage amplitude, and after comparing and performing PI processing on the reference voltage amplitude with the maximum stator voltage of the electric motor, the field-weakening compensation current is obtained; The d-axis current is obtained according to the q-axis current reference value of the electric motor, and the d-axis current is compensated by using the field-weakening compensation current to obtain the d-axis field-weakening current.

3. The control method for an electric motor according to claim 2, characterized in that, wherein, Obtaining the dq-axis voltage according to the q-axis field-weakening current and the limited d-axis field-weakening current includes: According to the q-axis field-weakening current and the limited d-axis field-weakening current, the dq-axis voltage is obtained through feedforward calculation; and / or, Obtaining the d-axis current according to the q-axis current reference value of the electric motor includes: In the speed outer loop of the electric motor, comparing and performing PI processing on the actual speed and the reference speed of the electric motor to obtain the q-axis current reference value of the electric motor; Performing MTPA processing on the q-axis current reference value of the electric motor to obtain the d-axis current of the electric motor; and / or, Making the d-axis field-weakening current, after being limited by a set characteristic current, obtain the limited d-axis field-weakening current; Making the limited d-axis field-weakening current, through the torque formula and the current limit circle restriction, obtain the q-axis current value after field-weakening.

4. The control method for an electric motor according to claim 3, characterized in that, As the rotational speed of the motor increases, the d-axis field-weakening current after limiting is reduced to a set minimum value, and the q-axis current is reversely compensated to continue field weakening, including: Determine the difference between the d-axis field-weakening current before limiting and the d-axis field-weakening current after limiting, denoted as the first difference; and, Add the first difference to the q-axis current value after field weakening, compare it with the actual q-axis current of the motor and perform PI processing to obtain the voltage vector angle of the motor; Determine the d-axis field-weakening current after limiting and the q-axis current value after field weakening; perform feedforward calculation using the d-axis field-weakening current after limiting and the q-axis current value after field weakening to obtain the actual value of the stator voltage of the motor; Accordingly, determine the dq-axis reference voltage vector of the motor according to the voltage vector angle and the maximum value of the stator voltage of the motor, including: Combine the voltage vector angle of the motor with the maximum value of the stator voltage of the motor, and after voltage amplitude operation, obtain the dq-axis reference voltage of the motor to obtain the voltage vector angle of the field-weakening control system of the motor.

5. A control device for a motor, Characterized in that, Including: A control unit configured to adopt a single q-axis current regulator in the field-weakening control system of the motor to freely switch between field-weakening traction and braking control under field-weakening conditions; The control unit is further configured to add a field-weakening compensation module to the control system of the single q-axis current regulator to perform field-weakening compensation processing on the d-axis and q-axis currents of the motor to obtain the d-axis field-weakening current; and add an out-of-control limiting and compensation module to perform out-of-control limiting and compensation processing on the d-axis field-weakening current of the motor to obtain the voltage vector angle of the field-weakening control system of the motor; wherein, the control unit adds an out-of-control limiting and compensation module to perform out-of-control limiting and compensation processing on the d-axis field-weakening current of the motor, including: in the out-of-control limiting and compensation module, the d-axis field-weakening current is clamped at a set characteristic current after limiting to obtain the d-axis field-weakening current after limiting; as the rotational speed of the motor increases, the field-weakening current after limiting is reduced to a set minimum value, and the q-axis current is reversely compensated to continue field weakening; The control unit is further configured to determine the dq-axis reference voltage vector of the motor according to the voltage vector angle and the maximum value of the stator voltage of the motor, so as to drive and control the system where the motor is located according to the dq-axis reference voltage vector.

6. The control device for a motor according to claim 5, Characterized in that, The control unit adds a field-weakening compensation module to the control system of the single q-axis current regulator to perform field-weakening compensation processing on the d-axis and q-axis currents of the motor to obtain the d-axis field-weakening current, including: In the field-weakening compensation module, obtain the dq-axis voltage according to the q-axis field-weakening current and the d-axis field-weakening current after limiting, then synthesize the reference voltage amplitude from the dq-axis voltage, and then compare the reference voltage amplitude with the maximum value of the stator voltage of the motor and perform PI processing to obtain the field-weakening compensation current; Obtain the d-axis current based on the q-axis current reference value of the motor, and compensate the d-axis current with the field-weakening compensation current to obtain the d-axis field-weakening current.

7. The control device of the motor according to claim 6, wherein, where, the control unit obtains the dq-axis voltage according to the q-axis field-weakening current and the limited d-axis field-weakening current, including: Obtain the dq-axis voltage through feed-forward calculation according to the q-axis field-weakening current and the limited d-axis field-weakening current; and / or, the control unit obtains the d-axis current according to the q-axis current reference value of the motor, including: In the speed outer loop of the motor, compare the actual speed of the motor with the reference speed and perform PI processing to obtain the q-axis current reference value of the motor; Perform MTPA processing on the q-axis current reference value of the motor to obtain the d-axis current of the motor; and / or, the control unit limits the d-axis field-weakening current through a set characteristic current limit to obtain the limited d-axis field-weakening current; Perform torque formula and current limit circle limitation on the limited d-axis field-weakening current to obtain the q-axis current value after field-weakening; wherein, as the speed of the motor increases, the control unit reduces the limited d-axis field-weakening current to a set minimum value, performs reverse compensation on the q-axis current, and continues field-weakening, including: Determine the difference between the d-axis field-weakening current before limitation and the limited d-axis field-weakening current, denoted as the first difference; and, Add the first difference to the q-axis current value after field-weakening, compare with the actual q-axis current of the motor and perform PI processing to obtain the voltage vector angle of the motor; Determine the limited d-axis field-weakening current and the q-axis current value after field-weakening; perform feed-forward calculation using the limited d-axis field-weakening current and the q-axis current value after field-weakening to obtain the actual value of the stator voltage of the motor; Correspondingly, the control unit determines the dq-axis reference voltage vector of the motor according to the voltage vector angle and the maximum value of the stator voltage of the motor, including: Combine the voltage vector angle of the motor with the maximum value of the stator voltage of the motor, perform voltage amplitude operation to obtain the dq-axis reference voltage of the motor, so as to obtain the voltage vector angle of the field-weakening control system of the motor.

8. A motor, wherein, including: The control device of the motor according to any one of claims 5 to 7.

9. A storage medium, wherein, The storage medium includes a stored program, wherein when the program runs, it controls the device where the storage medium is located to execute the control method of the motor according to any one of claims 1 to 4.

10. A processor, wherein, The processor is used to run a program, wherein when the program runs, it executes the control method of the motor according to any one of claims 1 to 4.

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