Weak magnetic control method and device thereof, surface-mounted permanent magnet synchronous motor and vehicle

Abstract

The application discloses a field weakening control method and device, a surface-mounted permanent magnet synchronous motor and a vehicle. The field weakening control method comprises the following steps: predicting the angular velocity of a motor in a next control period according to the angular velocity, the rotational inertia, the load torque and the torque current of the motor in a current control period; and determining the demagnetizing current applied to the motor in the next control period according to the rated angular velocity of the motor and the predicted angular velocity of the motor in the next control period. The reasonable distribution principle of the current vector in the excitation direction and the torque direction is ensured, the motor transient load capacity is improved, the motor high-speed load capacity and the anti-disturbance capacity are increased, and the motor operation efficiency is improved while the field weakening speed expansion is realized. Compared with the field weakening control mode of transmitting the PI control torque angle, the application adopts a real-time solving and updating mode, the tedious parameter adjusting process is omitted, the control deviation caused by the parameter mismatch is reduced, the control precision is higher, and unnecessary energy waste is avoided.

Description

Technical Field

[0001] This application relates to the field of electric drive, and more specifically to a field weakening control method and apparatus, a surface-mounted permanent magnet synchronous motor, and a vehicle. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) are widely used because they have no excitation windings, eliminate the need for brushes and slip rings, and can achieve electronic commutation. Compared to asynchronous motors, they are simpler in structure and more stable in operation. However, current adjustment methods for PMSMs result in poor control performance. Summary of the Invention

[0003] This application is made to address at least one of the aforementioned problems. According to a first aspect of this application, a field weakening control method for a surface-mounted permanent magnet synchronous motor is provided. The field weakening control method includes: predicting the angular velocity of the motor in the next control cycle based on the motor's angular velocity, moment of inertia, load torque, and torque current in the current control cycle; and determining a demagnetizing current to be applied to the motor in the next control cycle based on the motor's rated angular velocity and the predicted angular velocity in the next control cycle.

[0004] In one embodiment of this application, determining the demagnetizing current applied to the motor in the next control cycle based on the motor's rated angular velocity and the predicted angular velocity of the motor in the next control cycle includes: when the predicted angular velocity of the motor in the next control cycle is greater than the motor's rated angular velocity, predicting the demagnetizing current applied to the motor in the next control cycle based on the motor's angular velocity and torque current in the current control cycle; and determining the demagnetizing current applied to the motor in the next control cycle based on the demagnetizing current of the permanent magnets on the motor rotor and the predicted demagnetizing current applied to the motor in the next control cycle.

[0005] In one embodiment of this application, determining the demagnetizing current applied to the motor in the next control cycle based on the demagnetizing current of the permanent magnet on the motor rotor and the predicted demagnetizing current applied to the motor in the next control cycle includes: determining that the demagnetizing current applied to the motor in the next control cycle is equal to the predicted demagnetizing current applied to the motor in the next control cycle when the predicted demagnetizing current applied to the motor in the next control cycle is not greater than the demagnetizing current.

[0006] In one embodiment of this application, when the predicted demagnetizing current applied to the motor in the next control cycle is not greater than the product of the demagnetizing current and the margin coefficient, the demagnetizing current applied to the motor in the next control cycle is determined to be equal to the predicted demagnetizing current applied to the motor in the next control cycle; wherein the margin coefficient is greater than zero and less than 1.

[0007] In one embodiment of this application, determining the demagnetizing current applied to the motor in the next control cycle based on the demagnetizing current of the permanent magnet on the motor rotor and the predicted demagnetizing current applied to the motor in the next control cycle includes: determining that the demagnetizing current applied to the motor in the next control cycle is equal to the β*demagnetizing current when the predicted demagnetizing current applied to the motor in the next control cycle is greater than the β*demagnetizing current.

[0008] In one embodiment of this application, predicting the demagnetizing current applied to the motor in the next control cycle based on the angular velocity and torque current of the motor in the current control cycle includes: predicting the demagnetizing current applied to the motor in the next control cycle using the voltage limit circle equation based on the angular velocity and torque current of the motor in the current control cycle.

[0009] In one embodiment of this application, the step of predicting the demagnetizing current applied to the motor in the next control cycle using the voltage limit circle equation, based on the angular velocity and torque current of the motor in the current control cycle, includes:

[0010] Substituting the angular velocity and torque current of the motor in the current control cycle into the voltage limit circle equation shown below, the demagnetizing current applied to the motor in the next control cycle is calculated:

[0011]

[0012] Among them, U dc Indicates DC bus voltage; I q This represents the torque current of the motor during the current control cycle; I d This indicates the demagnetizing current applied to the motor in the next control cycle; L s Indicates the direct-axis and quadrature-axis inductance; P n W represents the extreme logarithm; m This indicates the angular velocity of the motor during the current control cycle; Flux represents the permanent magnet flux linkage on the motor rotor.

[0013] In one embodiment of this application, determining the demagnetizing current applied to the motor in the next control cycle based on the rated angular velocity of the motor and the predicted angular velocity of the motor in the next control cycle includes: determining that the demagnetizing current applied to the motor in the next control cycle is equal to zero when the predicted angular velocity of the motor in the next control cycle is not greater than the rated angular velocity of the motor.

[0014] In one embodiment of this application, predicting the angular velocity of the motor in the next control cycle based on the angular velocity, moment of inertia, load torque, and torque current of the motor in the current control cycle includes: using discrete domain motor mechanical motion equations to predict the angular velocity of the motor in the next control cycle based on the angular velocity, moment of inertia, load torque, and torque current of the motor in the current control cycle.

[0015] In one embodiment of this application, after determining the demagnetizing current applied to the motor in the next control cycle, the control method further includes: determining a limit value of the torque current of the motor in the next control cycle based on the rated current of the motor and the determined demagnetizing current applied to the motor in the next control cycle.

[0016] According to a second aspect of this application, a field weakening control device for a surface-mount permanent magnet synchronous motor is also provided. The field weakening control device includes a storage medium and a processor. The storage medium stores a computer program executed by the processor. When the computer program is executed by the processor, the processor causes the processor to perform any of the above-described field weakening control methods for a surface-mount permanent magnet synchronous motor.

[0017] According to a third aspect of this application, a surface-mounted permanent magnet synchronous motor is also provided, the surface-mounted permanent magnet synchronous motor including any of the above-mentioned field weakening control devices for surface-mounted permanent magnet synchronous motors.

[0018] According to a fourth aspect of this application, a vehicle is also provided, the vehicle comprising: a vehicle body, and any one of the above-described surface-mounted permanent magnet synchronous motors disposed on the vehicle body.

[0019] According to the field weakening control method and apparatus, surface-mounted permanent magnet synchronous motor, and vehicle provided in this application, the angular velocity of the motor in the next control cycle is predicted based on the angular velocity, moment of inertia, load torque, and torque current of the motor in the current control cycle. Then, based on the rated angular velocity of the motor and the predicted angular velocity of the motor in the next control cycle, the demagnetizing current applied to the motor in the next control cycle is determined. Through this method, the angular velocity of the motor in the next control cycle can be updated in real time, and the optimal demagnetizing current applied to the motor in the next control cycle can be determined based on the angular velocity of the motor in the next control cycle and the rated angular velocity of the motor. This ensures a reasonable distribution of the current vector in the excitation direction and torque direction, achieving field weakening and speed enhancement while improving the motor's transient load-carrying capacity, increasing the motor's high-speed load-carrying capacity and anti-disturbance capability, and improving the motor's operating efficiency. Compared to the field weakening control mode that transmits PI control torque angle, this application uses a real-time calculation and update method, eliminating the cumbersome parameter tuning process, reducing control deviations caused by parameter mismatch, achieving higher control accuracy, and avoiding unnecessary energy waste. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart illustrating a field weakening control method for a surface-mounted permanent magnet synchronous motor according to an embodiment of the present invention.

[0022] Figure 2 The flowchart illustrates a field weakening control method for a surface-mounted permanent magnet synchronous motor according to another embodiment of the present invention.

[0023] Figure 3 The flowchart illustrates a field weakening control method for a surface-mounted permanent magnet synchronous motor according to another embodiment of the present invention.

[0024] Figure 4 This is a schematic diagram illustrating the field weakening control principle of a surface-mounted permanent magnet synchronous motor according to an embodiment of the present invention.

[0025] Figure 5 This is a diagram illustrating the operating trajectory of a surface-mounted permanent magnet synchronous motor during field weakening control, according to an embodiment of the present invention.

[0026] Figure 6 This is a waveform diagram of motor speed and AC / DC current signals during motor operation, as shown in an embodiment of the present invention.

[0027] Figure 7This is a schematic block diagram illustrating the structure of a field weakening control device for a surface-mounted permanent magnet synchronous motor according to an embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention more apparent, exemplary embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely a part of the embodiments of the present invention, and not all of the embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein. Based on the embodiments of the present invention described herein, all other embodiments obtained by those skilled in the art without inventive effort should fall within the protection scope of the present invention.

[0029] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0030] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “compose” and / or “comprising,” when used in this specification, confirm the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0032] To fully understand this invention, a detailed structure will be presented in the following description to illustrate the technical solution proposed by this invention. Optional embodiments of the invention are described in detail below; however, in addition to these detailed descriptions, the invention may have other embodiments.

[0033] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0034] First, it is necessary to introduce the application scenario of the field weakening control method of the surface-mounted permanent magnet synchronous motor in this application. The field weakening control method of the surface-mounted permanent magnet synchronous motor is applied to the field weakening control process of the surface-mounted permanent magnet synchronous motor.

[0035] refer to Figure 1 This application provides a field weakening control method for a surface-mounted permanent magnet synchronous motor, the field weakening control method comprising:

[0036] Step 1: Based on the motor's angular velocity, moment of inertia, load torque, and torque current in the current control cycle, predict the motor's angular velocity in the next control cycle.

[0037] Step 2: Based on the motor's rated angular velocity and the predicted angular velocity of the motor in the next control cycle, determine the demagnetizing current to be applied to the motor in the next control cycle.

[0038] In the above scheme, the angular velocity of the motor in the next control cycle is predicted based on the motor's angular velocity, moment of inertia, load torque, and torque current in the current control cycle. Then, based on the motor's rated angular velocity and the predicted angular velocity in the next control cycle, the demagnetizing current applied to the motor in the next control cycle is determined. This method allows for real-time updates of the motor's angular velocity in the next control cycle, and the determination of the optimal demagnetizing current applied to the motor in the next control cycle, based on the motor's angular velocity and rated angular velocity. This ensures a reasonable distribution of the current vector in the excitation and torque directions, achieving field weakening and speed enhancement while improving the motor's transient load-carrying capacity, increasing its high-speed load-carrying and disturbance rejection capabilities, and improving its operating efficiency. Compared to the field weakening control mode that transmits PI control torque angle, this application uses a real-time calculation and update method, eliminating the tedious parameter tuning process, reducing control deviations caused by parameter mismatch, achieving higher control accuracy, and avoiding unnecessary energy waste. The following is a detailed description of each step in conjunction with the accompanying drawings.

[0039] First, refer to Figure 1 and Figure 4 Based on the motor's angular velocity, moment of inertia, load torque, and torque current in the current control cycle, the motor's angular velocity in the next control cycle is predicted.

[0040] The angular velocity of the motor in the current control cycle can be obtained through detection within the current control cycle, or it can be calculated based on the motor's angular velocity, moment of inertia, load torque, and torque current in the previous control cycle. Alternatively, the motor's angular velocity in the initial control cycle can be obtained through detection. Control can be initiated as soon as the motor starts, and the motor's angular velocity is zero in the initial control cycle. Then, using the motor's angular velocity, moment of inertia, load torque, and torque current from the current control cycle, the motor's angular velocity for the next control cycle can be predicted. Figure 4 ω in m (k) represents the angular velocity of the motor within the current control cycle, ω m (k+1) represents the predicted angular velocity of the motor in the next control cycle, k represents the current control cycle, and k+1 represents the next control cycle.

[0041] There are several ways to obtain the moment of inertia. For example, the moment of inertia of the motor can be detected once, and then used as a fixed value in the calculation process of each subsequent control cycle. Alternatively, the moment of inertia of the motor can be detected once in each control cycle, so that the calculation in each control cycle is based on the accurate moment of inertia value of the current control cycle, thereby improving the accuracy of the calculation. For instance, a motor moment of inertia identification module can be used to obtain the motor's moment of inertia in each control cycle. This module can use algorithms such as, but not limited to, discrete domain model reference adaptive or least squares algorithms to obtain the motor's moment of inertia in each control cycle. Figure 4 J in _est This represents the moment of inertia of the motor.

[0042] There are several ways to obtain the load torque. For example, a load torque observer can be used to obtain the motor's load torque within the current control cycle. This load torque observer can employ algorithms such as, but not limited to, reduced-order state observers or Romberg observers to obtain the motor's load torque for each control cycle. Figure 4 T in load_est This indicates the load torque of the motor.

[0043] Torque current can be obtained by directly measuring the motor's torque current within the current control cycle using sensors. The magnitude of the torque current is often related to the load torque within the current control cycle. For example... Figure 4 I in q (k) represents the motor torque current during the current control cycle, I q (k+1) represents the motor torque current in the next control cycle.

[0044] When predicting the motor's angular velocity for the next control cycle based on the motor's angular velocity, moment of inertia, load torque, and torque current in the current control cycle, various methods can be used. One such method is illustrated below.

[0045] For example, when predicting the motor's angular velocity in the next control cycle based on the motor's angular velocity, moment of inertia, load torque, and torque current in the current control cycle, the discrete-domain motor mechanical motion equations can be used to predict the motor's angular velocity in the next control cycle. (Reference) Figure 4 A virtual functional module, the angular velocity prediction module, can be set up. This module can calculate the angular velocity of the motor in the next control cycle by substituting the motor's torque current, angular velocity, moment of inertia, and load torque values ​​into the discrete-domain motor motion equations. The following is an example of a discrete-domain motor motion equation:

[0046]

[0047] Where k represents the current control cycle, k+1 represents the next control cycle, and ω m (k) represents the angular velocity of the motor within the current control cycle, ω m (k+1) represents the predicted angular velocity of the motor in the next control cycle. T s K represents the duration of the control cycle. t J represents the torque coefficient. _est T represents the moment of inertia of the motor. load_est This indicates the load torque of the motor.

[0048] It should be understood that the above is only an illustrative example of how to predict the angular velocity of the motor in the next control cycle. Other algorithms can also be used for prediction.

[0049] Next, refer to Figure 1 and Figure 4 Based on the motor's rated angular velocity and the predicted angular velocity in the next control cycle, the demagnetizing current applied to the motor in the next control cycle is determined. This ensures a reasonable distribution of the current vector in the excitation and torque directions, achieving field weakening and speed enhancement while improving the motor's transient load-carrying capacity, high-speed load capacity, and disturbance rejection capability, thus increasing motor operating efficiency. Compared to the field weakening control mode that uses PI control of torque angle, this application employs real-time calculation and updating, eliminating the tedious parameter tuning process, reducing control deviations caused by parameter mismatch, achieving higher control accuracy, and avoiding unnecessary energy waste. Figure 4 I in d (k+1) represents the demagnetizing current of the motor in the next control cycle.

[0050] Additionally, for example, after determining the demagnetizing current applied to the motor in the next control cycle, the control method may further include: determining a limit value for the motor's torque current in the next control cycle based on the motor's rated current and the determined demagnetizing current applied to the motor in the next control cycle. It should be explained that this torque current limit value refers to the maximum value of the torque current that can be applied in the next control cycle; that is, the actual torque current applied in the next control cycle cannot exceed the limit value for the motor's torque current in the next control cycle. The limit value I for the motor's torque current in the next control cycle is determined based on the motor's rated current and the determined demagnetizing current applied to the motor in the next control cycle. q When (k+1), the following formula can be used:

[0051]

[0052] When determining the demagnetizing current to be applied to the motor in the next control cycle based on the motor's rated angular velocity and the predicted angular velocity of the motor in the next control cycle, various methods can be used.

[0053] For example, refer to Figure 2 Based on the motor's rated angular velocity and the predicted angular velocity of the motor in the next control cycle, the demagnetizing current applied to the motor in the next control cycle is determined. This can include: if the predicted angular velocity of the motor in the next control cycle is not greater than the motor's rated angular velocity, the demagnetizing current applied to the motor in the next control cycle is determined to be zero. Figure 4 W0 in the figure represents the rated angular velocity of the motor.

[0054] For example, refer to Figure 4 A virtual zero-excitation control module can be set up. This module operates when the motor's angular velocity does not exceed the rated angular velocity, and the motor starts in maximum torque-to-current ratio mode. Since the surface-mounted permanent magnet synchronous motor has no reluctance torque, the demagnetizing current reference value I... d (k+1) = 0 (zero excitation control). At this time, the torque current limit value does not exceed the motor's rated current I. s The rated angular velocity W0 of the motor can be calculated using the direct-axis and quadrature-axis voltage balance equations.

[0055] For example, refer to Figure 2 and Figure 4The method for determining the demagnetizing current applied to the motor in the next control cycle based on the motor's rated angular velocity and the predicted angular velocity of the motor in the next control cycle may further include: when the motor's angular velocity in the predicted next control cycle is greater than the motor's rated angular velocity, the method for predicting the demagnetizing current applied to the motor in the next control cycle based on the motor's angular velocity and torque current in the current control cycle; and then, determining the demagnetizing current applied to the motor in the next control cycle based on the demagnetizing current of the permanent magnets on the motor rotor and the predicted demagnetizing current applied to the motor in the next control cycle.

[0056] In predicting the demagnetizing current to be applied to the motor in the next control cycle based on the motor's angular velocity and torque current in the current control cycle, various implementation methods can be adopted. One implementation method is described below as an example.

[0057] For example, the demagnetizing current applied to the motor in the next control cycle can be predicted using the voltage limit circle equation based on the motor's angular velocity and torque current in the current control cycle, so as to quickly and accurately predict the demagnetizing current applied to the motor in the next control cycle.

[0058] When predicting the demagnetizing current to be applied to the motor in the next control cycle based on the motor's angular velocity and torque current during the current control cycle, using the voltage limit circle equation, various methods can be employed. One such method is illustrated below. For example, refer to... Figure 4 A virtual voltage limit circle calculation module can be set up and put into operation when the motor's angular velocity exceeds the rated angular velocity. By substituting the motor's angular velocity in the current control period and the torque current corresponding to the load torque in the current control cycle (i.e., the torque current in this control cycle) into the voltage limit circle equation, the required demagnetizing current I can be calculated. d (k+1).

[0059] Specifically, by substituting the motor's angular velocity and torque current within the current control cycle into the voltage limit circle equation shown below, the demagnetizing current applied to the motor in the next control cycle can be calculated:

[0060]

[0061] Among them, U dc Indicates DC bus voltage; I q Indicates the motor torque current during the current control cycle; I d This indicates the demagnetizing current applied to the motor in the next control cycle; L s Indicates the direct-axis and quadrature-axis inductance; P n W represents the extreme logarithm; m It represents the angular velocity of the motor within the current control cycle; Flux represents the permanent magnet flux linkage on the motor rotor.

[0062] There are several ways to derive the voltage limit circle equation. The following is an exemplary method for deriving the voltage limit circle equation. First, the following shows a method for writing the direct-axis voltage balance equation:

[0063]

[0064] Among them, R s Indicates armature resistance, L d =L q =L s Indicates the direct-axis and quadrature-axis inductance, P n Represents the extreme logarithm, W m ω represents the angular velocity of the motor, and Flux represents the flux linkage of the permanent magnets on the motor rotor.

[0065] When the predicted angular velocity of the motor reaches its rated angular velocity in the next control cycle, the rotating back EMF component accounts for a very large proportion, and the voltage drop due to inductance and resistance can be ignored. The above-mentioned AC-DC axis voltage balance equation can be transformed into the following voltage limit circle equation:

[0066]

[0067] Among them, U dc This represents the DC bus voltage. The formula is as follows: Figure 5 The center of the circle is (0, -Flux / L) d ), radius is The voltage limit circle. Then, based on the motor torque current I within the current control cycle. q (k), and the angular velocity W of the motor m It can predict in real time the demagnetizing current I required by the motor in the next control cycle. d (k+1).

[0068] It should be understood that, in addition to the methods shown above, other methods can be used to predict the demagnetizing current applied to the motor in the next control cycle based on the motor's angular velocity and torque current in the current control cycle.

[0069] When determining the demagnetizing current to be applied to the motor in the next control cycle based on the demagnetizing current of the permanent magnets on the motor rotor and the predicted demagnetizing current to be applied to the motor in the next control cycle, various methods can be used.

[0070] For example, refer to Figure 3Based on the demagnetizing current of the permanent magnets on the motor rotor and the predicted demagnetizing current to be applied to the motor in the next control cycle, the demagnetizing current to be applied to the motor in the next control cycle is determined. This can include: if the predicted demagnetizing current to be applied to the motor in the next control cycle is not greater than the demagnetizing current, the demagnetizing current to be applied to the motor in the next control cycle is determined to be equal to the predicted demagnetizing current to be applied to the motor in the next control cycle. This ensures that the demagnetizing current is not greater than the demagnetizing current. There are various methods for determining the demagnetizing current of the permanent magnets on the motor rotor; for example, the demagnetizing current of the permanent magnets on the motor rotor can be equal to Flux / L. d .

[0071] In some embodiments, when the demagnetizing current applied to the motor in the predicted next control cycle is not greater than the product of the demagnetizing current and the margin coefficient, the demagnetizing current applied to the motor in the next control cycle is determined to be equal to the predicted demagnetizing current applied to the motor in the next control cycle; wherein the margin coefficient is greater than zero and less than 1. For example, β is used to represent the margin coefficient, where 0 < β < 1. To prevent permanent demagnetization of the permanent magnet, the demagnetizing current maintains a certain margin, ensuring that the demagnetizing current is less than the demagnetizing current. For example, the margin coefficient β can take any value between 0 and 1, such as 0.9.

[0072] For example, refer to Figure 4 A virtual variable flux control module can be set up. When the demagnetizing current applied to the motor in the predicted next control cycle is no greater than β*demagnetizing current, field weakening mode 1 is adopted, and the variable flux control module is put into operation. As the angular velocity of the motor continues to increase, the demagnetizing current I... d The magnitude of (k+1) continues to increase.

[0073] For example, refer to Figure 3 The method of determining the demagnetizing current to be applied to the motor in the next control cycle based on the demagnetizing current of the permanent magnet on the motor rotor and the predicted demagnetizing current to be applied to the motor in the next control cycle may further include: when the predicted demagnetizing current to be applied to the motor in the next control cycle is greater than β*demagnetizing current, determining that the demagnetizing current to be applied to the motor in the next control cycle is equal to β*demagnetizing current.

[0074] For example, refer to Figure 4 A virtual constant flux control module can be set up. When the demagnetizing current applied to the motor in the predicted next control cycle is greater than β*demagnetizing current, field weakening mode 2 is adopted, and the constant flux control module is put into operation. The torque current limit value in field weakening mode 2 in the next control cycle is determined. Where Is is the rated current of the motor.

[0075] The following combination Figure 4 , Figure 5 and Figure 6This paper provides an example of the field weakening control method used in each process of a motor from startup to the gradual increase of its angular velocity.

[0076] like Figure 6 As shown, at t=0, the motor first starts at the maximum torque-to-current ratio (MTPA), corresponding to... Figure 5 In segment OA, the input commands to the AC and DC axis current loop controller are: demagnetizing current I... d =0, torque current I q This is the speed loop limiting output value. As the speed error decreases, the torque current I... q Gradually decaying. At time t = t1, the motor angular velocity W for the next control cycle is predicted by first substituting the moment of inertia and load torque into the discrete-domain motor mechanical motion equations. m (k+1). This means the motor starts at its maximum torque-to-current ratio, and its angular velocity continuously increases. The motor's moment of inertia and load torque can be observed, and the angular velocity W of the motor in the current control cycle is... m (k) Torque Current I q (k) The moment of inertia and load torque are input into the discrete domain motor mechanical motion equations, which can predict the angular velocity of the motor in the next control cycle in real time.

[0077] refer to Figure 6 When the angular velocity of the motor increases to the rated angular velocity W0 (corresponding to...) Figure 5 At point A, the motor's angular velocity exceeds the maximum value under the current load condition. At this point, the rotating back EMF approaches the DC bus voltage, making it difficult for the motor's angular velocity to continue increasing. Therefore, the system switches to field weakening mode 1. The demagnetizing current I required for the next control cycle can be calculated using the voltage limit circle equation. d (k+1), during this process, the direct-axis demagnetizing current is updated in real time (variable flux control), and then the torque current limit value is determined.

[0078]

[0079] refer to Figure 5 At this point, the control mode switches from maximum torque-to-current ratio (OA running trajectory) to field weakening mode 1 (AB running trajectory). By substituting the angular velocity and torque current of the current control cycle into the voltage limit circle equation, the demagnetizing current I required by the motor in the next control cycle can be predicted. d (k+1). The demagnetizing current I at this time d (k+1) is still much smaller than β* demagnetizing current. That is, if the predicted motor angular velocity for the next control cycle is greater than the motor's rated angular velocity W0, the system quickly switches to field weakening mode 1 and continues to predict the motor angular velocity for each control cycle, continuously updating the demagnetizing current I required for the next control cycle. d (k+1).

[0080] Under field weakening mode 1, as the angular velocity of the motor further increases, the amplitude of the demagnetizing current continuously increases. At t = t2, the amplitude of the demagnetizing current increases in the opposite direction to -β*Flux / L. d At this time, the control mode switches to field weakening mode 2, maintaining the demagnetizing current I. d (k+1)=-β*Flux / L d Unchanged (constant flux control), torque current limit value is To further increase the speed, the torque current I needs to be reduced. q+1 At this time, the motor's operating range is Figure 5 The BC segment is shown. That is, if the demagnetizing current I in the next control cycle... d (k+1) is close to the demagnetizing current Flux / L of the permanent magnet on the motor rotor. d The control mode is switched from field weakening mode 1 to field weakening mode 2, and the demagnetizing current is maintained at I. d (k+1)=-β*Flux / L d constant.

[0081] In the various embodiments shown above, the angular velocity of the motor in the next control cycle is predicted based on the motor's angular velocity, moment of inertia, load torque, and torque current in the current control cycle. Then, the demagnetizing current applied to the motor in the next control cycle is determined based on the motor's rated angular velocity and the predicted angular velocity in the next control cycle. This method allows for real-time updating of the motor's angular velocity in the next control cycle, and the determination of the optimal demagnetizing current applied to the motor in the next control cycle based on the motor's angular velocity and rated angular velocity. This ensures a reasonable distribution of the current vector in the excitation and torque directions, maximizing the required torque current and effectively improving the motor's operating efficiency above its rated angular velocity. It achieves field weakening and speed enhancement while improving the motor's transient load-carrying capacity, increasing its high-speed load-carrying and disturbance rejection capabilities, and improving overall motor operating efficiency. Compared to the field weakening control mode that transmits PI control torque angle, this application uses a real-time calculation and update method, eliminating the cumbersome parameter tuning process, reducing control deviations caused by parameter mismatch, achieving higher control accuracy, and avoiding unnecessary energy waste. Furthermore, the field weakening control strategy adopted in this application predicts and updates the required demagnetizing current and torque current in real time through analytical methods, which can be applied to complex load conditions where the disturbance torque varies with time.

[0082] contrast Figure 6Without the field weakening control shown, the motor's angular velocity, once reaching its rated angular velocity, struggles to increase significantly. However, with the field weakening control strategy described in this application, the motor can quickly switch to field weakening mode 1 after completing MTPA startup, improving its angular velocity response and extending its operating range above the rated angular velocity. It can be seen that the field weakening control strategy shown in this embodiment offers higher control accuracy compared to traditional PI torque angle control, eliminates the need for complex parameter tuning, avoids control deviations caused by parameter mismatch, and can update the required demagnetizing current in real time, rationally allocating the current vector and improving the motor's high-speed operating efficiency and anti-disturbance capability.

[0083] Furthermore, this application embodiment also provides a field weakening control device for a surface-mount permanent magnet synchronous motor. The field weakening control device includes a storage medium and a processor. The storage medium stores a computer program that is executed by the processor. When the computer program is executed by the processor, it causes the processor to execute any of the above-described field weakening control methods for surface-mount permanent magnet synchronous motors.

[0084] Figure 7 A schematic block diagram of a field weakening control device 100 for a surface-mount permanent magnet synchronous motor according to an embodiment of this application is shown. Figure 7 As shown, the field weakening control device 100 for a surface-mount permanent magnet synchronous motor according to an embodiment of this application may include a storage medium 110 and a processor 120. The storage medium 110 stores a computer program executed by the processor 120. When the computer program is executed by the processor 120, the processor 120 performs the field weakening control method for the surface-mount permanent magnet synchronous motor described above according to an embodiment of this application. Exemplarily, the field weakening control device 100 for the surface-mount permanent magnet synchronous motor can be deployed on the motor controller of the surface-mount permanent magnet synchronous motor. When the surface-mount permanent magnet synchronous motor is applied to a vehicle, the motor controller can be the MCU of the vehicle terminal. Those skilled in the art can understand the specific operation of the deployment device for the field weakening control device 100 for the surface-mount permanent magnet synchronous motor according to the embodiments of this application in conjunction with the foregoing content; for simplicity, it will not be described again here.

[0085] The storage medium may include, for example, a memory card for a smartphone, a storage component for a tablet computer, a hard drive for a personal computer, a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a portable compact disc read-only memory (CD-ROM), a USB storage device, or any combination of the above storage media. A computer-readable storage medium may be any combination of one or more computer-readable storage media.

[0086] Furthermore, this application also provides a surface-mount permanent magnet synchronous motor, which includes a field weakening control device for any of the aforementioned surface-mount permanent magnet synchronous motors. The surface-mount permanent magnet synchronous motor may further include a stator, a rotor, and an output shaft connected to the rotor, wherein permanent magnets are also disposed on the rotor. This surface-mount permanent magnet synchronous motor can be applied to vehicles such as, but not limited to, electric vehicles, and also to industrial manufacturing processes such as, but not limited to, automated production lines.

[0087] Furthermore, this application also provides a vehicle comprising: a vehicle body and any of the aforementioned surface-mounted permanent magnet synchronous motors mounted on the vehicle body. The vehicle can be, but is not limited to, an electric vehicle or a gasoline-powered vehicle. The vehicle body may include structures such as a frame, wheels, a transmission, and a steering wheel, and any of the aforementioned surface-mounted permanent magnet synchronous motors is mounted on the vehicle body.

[0088] The present invention has been described through the above embodiments. However, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, those skilled in the art will understand that the present invention is not limited to the above embodiments, and many more variations and modifications can be made based on the teachings of the present invention, all of which fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A field weakening control method for a surface-mounted permanent magnet synchronous motor, characterized in that, include: Based on the motor's angular velocity, moment of inertia, load torque, and torque current in the current control cycle, predict the motor's angular velocity in the next control cycle. Based on the rated angular velocity of the motor and the predicted angular velocity of the motor in the next control cycle, determine the demagnetizing current applied to the motor in the next control cycle; The step of determining the demagnetizing current applied to the motor in the next control cycle based on the motor's rated angular velocity and the predicted angular velocity of the motor in the next control cycle includes: If the angular velocity of the motor is greater than the rated angular velocity of the motor in the predicted next control cycle, the demagnetizing current to be applied to the motor in the next control cycle is predicted based on the angular velocity and torque current of the motor in the current control cycle. The demagnetizing current applied to the motor in the next control cycle is determined based on the demagnetizing current of the permanent magnet on the motor rotor and the predicted demagnetizing current applied to the motor in the next control cycle.

2. The field weakening control method as described in claim 1, characterized in that, The step of determining the demagnetizing current applied to the motor in the next control cycle based on the demagnetizing current of the permanent magnet on the motor rotor and the predicted demagnetizing current applied to the motor in the next control cycle includes: If the predicted demagnetizing current applied to the motor in the next control cycle is not greater than the demagnetizing current, then the demagnetizing current applied to the motor in the next control cycle is determined to be equal to the predicted demagnetizing current applied to the motor in the next control cycle.

3. The field weakening control method as described in claim 2, characterized in that, When the predicted demagnetizing current applied to the motor in the next control cycle is not greater than the product of the demagnetizing current and the margin coefficient, the demagnetizing current applied to the motor in the next control cycle is determined to be equal to the predicted demagnetizing current applied to the motor in the next control cycle; wherein the margin coefficient is greater than zero and less than 1.

4. The field weakening control method as described in claim 1, characterized in that, The step of determining the demagnetizing current applied to the motor in the next control cycle based on the demagnetizing current of the permanent magnet on the motor rotor and the predicted demagnetizing current applied to the motor in the next control cycle includes: When the predicted demagnetizing current applied to the motor in the next control cycle is greater than β*demagnetizing current, it is determined that the demagnetizing current applied to the motor in the next control cycle is equal to β*demagnetizing current, where β is a margin coefficient.

5. The field weakening control method as described in claim 1, characterized in that, The step of predicting the demagnetizing current to be applied to the motor in the next control cycle based on the angular velocity and torque current of the motor in the current control cycle includes: Based on the angular velocity and torque current of the motor in the current control cycle, the demagnetizing current to be applied to the motor in the next control cycle is predicted using the voltage limit circle equation.

6. The field weakening control method as described in claim 5, characterized in that, The step of predicting the demagnetizing current to be applied to the motor in the next control cycle based on the angular velocity and torque current of the motor in the current control cycle, using the voltage limit circle equation, includes: Substituting the angular velocity and torque current of the motor in the current control cycle into the voltage limit circle equation shown below, the demagnetizing current applied to the motor in the next control cycle is calculated: Among them, U dc Indicates the DC bus voltage; I q This represents the torque current of the motor during the current control cycle; I d This indicates the demagnetizing current applied to the motor in the next control cycle; L s Indicates the direct-axis and quadrature-axis inductance; P n Represents the extreme logarithm; W m This indicates the angular velocity of the motor within the current control cycle; Flux refers to the flux linkage of permanent magnets on the rotor of an electric motor.

7. The field weakening control method as described in claim 1, characterized in that, The step of determining the demagnetizing current applied to the motor in the next control cycle based on the motor's rated angular velocity and the predicted angular velocity of the motor in the next control cycle includes: If the angular velocity of the motor is not greater than the rated angular velocity of the motor in the predicted next control cycle, the demagnetizing current applied to the motor in the next control cycle is determined to be zero.

8. The field weakening control method as described in claim 1, characterized in that, The step of predicting the angular velocity of the motor in the next control cycle based on the motor's angular velocity, moment of inertia, load torque, and torque current in the current control cycle includes: Based on the motor's angular velocity, moment of inertia, load torque, and torque current in the current control cycle, the discrete domain motor mechanical motion equations are used to predict the motor's angular velocity in the next control cycle.

9. The field weakening control method as described in claim 1, characterized in that, After determining the demagnetizing current to be applied to the motor in the next control cycle, the control method further includes: Based on the rated current of the motor and the determined demagnetizing current applied to the motor in the next control cycle, the limit value of the torque current of the motor in the next control cycle is determined.

10. A field weakening control device for a surface-mounted permanent magnet synchronous motor, characterized in that, include: A storage medium and a processor, wherein the storage medium stores a computer program executed by the processor, the computer program, when executed by the processor, causes the processor to perform a field weakening control method for a surface-mounted permanent magnet synchronous motor as described in any one of claims 1 to 9.

11. A surface-mounted permanent magnet synchronous motor, characterized in that, include: The field weakening control device for a surface-mounted permanent magnet synchronous motor as described in claim 10.

12. A vehicle, characterized in that, include: Vehicle body; The surface-mounted permanent magnet synchronous motor as described in claim 11 is mounted on the vehicle body.

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