Control method and control system of asynchronous motor, vehicle and storage medium

Abstract

The application provides a control method and system of an asynchronous motor, a vehicle and a storage medium. The method comprises: in response to the current amplitude of the asynchronous motor being greater than a preset threshold and the current flowing through the inverter of the asynchronous motor being a direct current, selecting a target slip from a slip set corresponding to a given torque, the sum of the target slip and the electrical angular velocity of the motor being not 0; determining a current direct-axis current expected value and a current cross-axis current expected value according to the target slip and the given torque; and controlling the asynchronous motor to rotate according to the current direct-axis current expected value and the current cross-axis current expected value. The embodiment realizes protection of the switching device of the inverter.

Description

Technical Field

[0001] This application relates to the field of motor control technology, and in particular to a control method, control system, vehicle, and storage medium for an asynchronous motor. Background Technology

[0002] An asynchronous motor, also known as an induction motor, is an AC motor that converts electromechanical energy into mechanical energy by generating electromagnetic torque through the interaction between the rotating magnetic field in the air gap and the induced current in the rotor windings.

[0003] The inventors discovered that when an asynchronous motor is in certain specific power generation conditions, the current flowing through the switching devices in the inverter of the asynchronous motor is direct current. Compared with alternating current, a single switching device in the inverter may be in a working state for a long time, and the heat generation may increase dramatically, which may lead to damage to the switching device in severe cases. Summary of the Invention

[0004] In view of this, this application provides a control method, control system, vehicle, and storage medium for an asynchronous motor.

[0005] Specifically, this application is implemented through the following technical solution:

[0006] According to a first aspect of the embodiments of this application, a control method for an asynchronous motor is provided, comprising:

[0007] In response to the asynchronous motor's current amplitude being greater than a preset threshold and the inverter current flowing through the asynchronous motor being DC current, a target slip is selected from the slip set corresponding to a given torque, wherein the sum of the target slip and the motor's electric angular velocity is not 0.

[0008] Based on the target slip and the given torque, determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current;

[0009] The asynchronous motor is controlled to rotate based on the current expected value of the direct-axis current and the current expected value of the quadrature-axis current.

[0010] Optionally, the current amplitude of the asynchronous motor is determined based on the previous expected value of the direct-axis current and the previous expected value of the quadrature-axis current of the asynchronous motor; or the current amplitude of the asynchronous motor is determined based on the observed value of the direct-axis current and the observed value of the quadrature-axis current of the asynchronous motor.

[0011] Optionally, it also includes:

[0012] Obtain the current slip and electrical angular velocity of the asynchronous motor;

[0013] If the sum of the current slip and electrical angular velocity of the asynchronous motor is close to 0, the current flowing through the inverter of the asynchronous motor is determined to be a direct current.

[0014] Optionally, determining the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the target slip and the given torque includes:

[0015] PI adjustment is performed based on the difference between the target slip and the current slip of the asynchronous motor to obtain the target stator flux vector;

[0016] Based on the target stator flux linkage vector and the given torque, determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current.

[0017] Optionally, determining the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the target slip and the given torque includes:

[0018] The target stator flux vector is obtained based on the target slip and the pre-calibrated mapping relationship between different slips and the stator flux vector.

[0019] Based on the target stator flux linkage vector and the given torque, determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current.

[0020] Optionally, determining the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the target stator flux linkage vector and the given torque includes:

[0021] Obtain the constant stator flux linkage curve corresponding to the target stator flux linkage vector and the constant torque curve corresponding to the given torque; the constant stator flux linkage curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same target stator flux linkage vector, and the constant torque curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same given torque;

[0022] Based on the intersection of the constant stator flux linkage curve and the constant torque curve, determine the current expected value of the direct axis current and the current expected value of the quadrature axis current.

[0023] Optionally, determining the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the target slip and the given torque includes:

[0024] Obtain the constant slip curve for the target slip and the constant torque curve corresponding to the given torque; the constant slip curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same target slip; the constant torque curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same given torque;

[0025] Based on the intersection of the constant slip curve and the constant torque curve, determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current.

[0026] According to a second aspect of the embodiments of this application, a control system for an asynchronous motor is provided, including a controller, an inverter, and an asynchronous motor;

[0027] The controller is configured to perform the method described in any one of the first aspects; and to send a switching signal to the inverter based on the current expected value of the direct-axis current and the current expected value of the quadrature-axis current;

[0028] The inverter is used to output three-phase line voltage according to the switching signal to drive the asynchronous motor to rotate.

[0029] According to a third aspect of the embodiments of this application, a vehicle is provided, including a control system for the asynchronous motor described in the second aspect.

[0030] According to a fourth aspect of the embodiments of this application, a computer-readable storage medium is provided, on which computer instructions are stored, wherein when executed by a processor, the computer instructions implement the steps of the method described in any one of the first aspects.

[0031] The technical solutions provided by the embodiments of this disclosure may include the following beneficial effects:

[0032] In this embodiment, in response to the asynchronous motor's current amplitude exceeding a preset threshold and the inverter current flowing through the asynchronous motor being direct current, a target slip is selected from the slip set corresponding to a given torque. The sum of the target slip and the motor's electrical angular velocity is not zero. Then, based on the target slip and the given torque, the current expected value of the direct-axis current and the current expected value of the quadrature-axis current are determined. Based on the current expected values ​​of the direct-axis current and the current expected values ​​of the quadrature-axis current, the asynchronous motor is controlled to rotate. By redetermining the target slip and using it to determine the asynchronous motor, the inverter current flowing through the asynchronous motor is made alternating current, thereby avoiding excessive heat generation in the inverter's switching devices due to direct current and protecting the switching devices in the inverter.

[0033] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0034] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0035] Figure 1 This is a schematic diagram of the structure of a control system for an asynchronous motor, as illustrated in an exemplary embodiment of this application.

[0036] Figure 2This is a schematic diagram illustrating a vector control process for an asynchronous motor according to an exemplary embodiment of this application.

[0037] Figure 3 This is a flowchart illustrating an exemplary embodiment of the control method for an asynchronous motor.

[0038] Figure 4 This is a schematic diagram illustrating the constant torque curve, constant stator flux linkage curve, constant slip curve, and MTPA curve on the IdIq plane in an exemplary embodiment of this application.

[0039] Figure 5 This is a schematic diagram illustrating, in an exemplary embodiment of this application, the determination of the current desired value of the direct-axis current and the current desired value of the quadrature-axis current by PI adjustment.

[0040] Figure 6 This is a flowchart illustrating another asynchronous motor control method according to an exemplary embodiment of this application. Detailed Implementation

[0041] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0042] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0043] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0044] The inventors discovered that when an asynchronous motor is under certain specific power generation conditions, such as when the asynchronous motor's speed is positive (i.e., the asynchronous motor's electrical angular velocity (speed and electrical angular velocity can be converted to each other) is positive), and the asynchronous motor's slip is negative, and the sum of the two is 0, the current flowing through the switching devices in the inverter of the asynchronous motor is direct current. Compared to alternating current, a single switching device in the inverter may be in a working state for a long time, and the heat generation may increase dramatically, which may lead to damage to the switching device in severe cases.

[0045] To address the problems in related technologies, this application provides a control method for an asynchronous motor. In response to the asynchronous motor's current amplitude exceeding a preset threshold and the inverter current flowing through the asynchronous motor being direct current (DC), a target slip is selected from a set of slips corresponding to a given torque. The sum of the target slip and the motor's electrical angular velocity is not zero. Then, based on the target slip and the given torque, the current expected value of the direct-axis current and the current expected value of the quadrature-axis current are determined. Based on the current expected values ​​of the direct-axis current and the quadrature-axis current, the asynchronous motor is controlled to rotate. This embodiment, by redetermining the target slip and using it to determine the asynchronous motor, ensures that the inverter current flowing through the asynchronous motor is alternating current (AC), thereby avoiding excessive heat generation in the inverter's switching devices due to DC current and protecting the switching devices in the inverter.

[0046] In one exemplary embodiment, please refer to Figure 1 , Figure 1 A control system for an asynchronous motor is illustrated, comprising a controller, an inverter, and the asynchronous motor. The controller utilizes Field-Oriented Control (FOC, also known as vector control) to control the asynchronous motor. Through coordinate transformation, the control of the three-phase AC current is converted into the control of the q-axis (quadrature axis) current generating torque and the d-axis (direct axis) current generating the magnetic field, achieving independent control of torque and excitation. The FOC algorithm works as follows: first, the rotor's angular position is measured, thus determining the direction of the rotor's magnetic field. Based on the rotor's position, the desired stator flux linkage vector can be calculated. Finally, the desired stator flux linkage vector is synthesized by controlling the three-phase currents. The stator flux linkage vector is decomposed into two orthogonal vectors: one along the direction of the rotor flux linkage vector (called the direct axis, denoted by d), and the other perpendicular to the direction of the rotor flux linkage vector (called the quadrature axis, denoted by q).

[0047] Please see Figure 2This example illustrates the control process of an asynchronous motor implemented by a controller based on the Field Oriented Control (FOC, also known as vector control) method.

[0048] 1. The inverter outputs three-phase line voltages Ua, Ub and Uc. Two phase values ​​are collected, transformed by formula and then by Clark transformation, and then expressed as Uα and Uβ in the two-phase stationary coordinate system.

[0049] 2. Collect the three-phase currents Ia, Ib and Ic of the asynchronous motor. After Clark transformation, they are Iα and Iβ in the two-phase stationary coordinate system, respectively. After Park transformation, they are the direct-axis current observation value Id and the quadrature-axis current observation value Iq in the synchronous rotating coordinate system, respectively.

[0050] 3. Based on the currents Iα and Iβ in the two-phase stationary coordinate system and the voltages Uα and Uβ in the two-phase stationary coordinate system, the electric angular velocity ω1 of the asynchronous motor is estimated.

[0051] 4. Calculate the slip ω2 based on the given expected value of the direct-axis current Id* and the given expected value of the quadrature-axis current Iq*.

[0052] 5. The electric angular velocity ω1 and slip ω2 are added together by an adder and then integrated by an integrator to obtain the synchronous rotation angle θ. The synchronous rotation angle θ is used for Park transformation and inverse Park transformation.

[0053] 6. The expected value of the direct-axis current Id* and the observed value of the direct-axis current Id are subtracted by a subtractor, and then the direct-axis voltage Ud is output after PI regulation.

[0054] 7. The expected value of quadrature-axis current Iq* and the observed value of quadrature-axis current Iq are subtracted by a subtractor, and then the quadrature-axis voltage Uq is output after PI regulation.

[0055] 8. The direct-axis voltage Ud and quadrature-axis voltage Uq in the synchronous rotating coordinate system are transformed by Park inverse transformation to obtain Uα and Uβ in the stationary coordinate system; after SVPWM, Uα and Uβ are subjected to space vector pulse width modulation, and the PWM wave is output to the inverter module, which drives the asynchronous motor.

[0056] When the sum of the electric angular velocity ω1 and the slip ω2 is 0, the current flowing through the switching devices in the inverter of the asynchronous motor is DC current. Compared with AC current, a single switching device in the inverter may be in a working state for a long time, and the heat generation may increase dramatically, which may lead to damage to the switching device in severe cases.

[0057] For the above issues, please refer to Figure 3 This application provides a control method for an asynchronous motor, which can be implemented by... Figure 1 The method is executed by the controller in the system, and includes:

[0058] In step S101, in response to the current amplitude of the asynchronous motor being greater than a preset threshold and the current flowing through the inverter of the asynchronous motor being a DC current, a target slip is selected from the slip set corresponding to the given torque, wherein the sum of the target slip and the electric angular velocity of the motor is not 0.

[0059] In step S102, the current expected value of direct-axis current and the current expected value of quadrature-axis current are determined based on the target slip and the given torque.

[0060] In step S103, the asynchronous motor is controlled to rotate according to the current expected value of the direct axis current and the current expected value of the quadrature axis current.

[0061] In this embodiment, considering that the current amplitude is large and the current flowing through the inverter of the asynchronous motor is DC current, the switching devices in the inverter will experience a surge in heat generation. To protect the inverter, when this situation occurs, a target slip that is not zero when the sum of the electric angular velocity and the motor's electric angular velocity is reselected, and the current expected value of the direct-axis current and the current expected value of the quadrature-axis current are re-determined using the target slip and the given torque. This is used to drive the asynchronous motor, so that the current flowing through the inverter of the asynchronous motor is AC current, thereby avoiding excessive heat generation of the switching devices in the inverter due to DC current and protecting the switching devices in the inverter.

[0062] For example, regarding the determination of the current amplitude of an asynchronous motor: the controller can determine the current amplitude based on the expected value of the previous direct-axis current of the asynchronous motor (e.g., Figure 2 (Id*) and the previous quadrature axis current expectation (e.g. Figure 2 The current amplitude of the asynchronous motor is determined by Iq*). Let the current amplitude be I, then we have Alternatively, the controller can acquire the direct-axis current observation of the asynchronous motor (e.g., Figure 2 (Id) and cross-axis current observations (such as Figure 2 Then, based on the observed direct-axis current and quadrature-axis current of the asynchronous motor, the current amplitude of the asynchronous motor is determined. Let the current amplitude be I, then we have... .

[0063] Regarding whether the current flowing through the inverter of the asynchronous motor is direct current, two possible implementations are illustrated here.

[0064] In one possible implementation, the controller can determine whether the current flowing through the inverter of the asynchronous motor is a direct current by detecting the magnitude and direction of the current of the asynchronous motor; wherein, a current whose magnitude and direction do not change with time is called a direct current.

[0065] In another possible implementation, the inventors discovered that when the sum of the slip and electrical angular velocity of the asynchronous motor is 0, the current flowing through the inverter of the asynchronous motor is a direct current (DC). The controller can then obtain the current slip and electrical angular velocity of the asynchronous motor; and then determine whether the sum of the current slip and electrical angular velocity is close to 0. If the sum is close to 0, it can be determined that the current flowing through the inverter of the asynchronous motor is a DC current; if the sum is not close to 0, it can be determined that the current flowing through the inverter of the asynchronous motor is an alternating current (AC).

[0066] For example, the current slip of the asynchronous motor can be determined based on the previous expected value of the direct-axis current and the previous expected value of the quadrature-axis current of the asynchronous motor.

[0067] Please see Figure 2 In the illustrated embodiment, the determination of the electrical angular velocity includes: acquiring the values ​​of two phases of the three-phase line voltages Ua, Ub, and Uc output by the inverter, transforming them using a formula and then performing a Clark transformation to obtain Uα and Uβ in the stationary coordinate system; and acquiring the three-phase currents Ia, Ib, and Ic of the asynchronous motor, transforming them using a Clark transformation to obtain Iα and Iβ in the stationary coordinate system, and estimating the electrical angular velocity ω1 of the asynchronous motor based on the currents Iα and Iβ in the two-phase stationary coordinate system and the voltages Uα and Uβ in the two-phase stationary coordinate system.

[0068] In some embodiments, considering that the current amplitude of the asynchronous motor is large and the current flowing through the inverter of the asynchronous motor is DC current, the switching devices in the inverter need to withstand excessive heat caused by the large DC current, which may damage the switching devices in the inverter in severe cases.

[0069] Please see Figure 4 , Figure 4 The diagram shows the constant torque curve, constant stator flux linkage curve, constant slip curve, and MTPA curve on the IdIq plane; where the horizontal axis represents the direct-axis current value Id, and the vertical axis represents the quadrature-axis current value Iq. The constant torque curve indicates multiple different Id-Iq combinations corresponding to the same torque; for example... Figure 4The diagram shows isotorque curves with torque values ​​of {-2, -12, -22, -32, -42, -52, ..., -332, -342}. The isotorque curves indicate multiple different Id-Iq combinations corresponding to the same stator flux linkage vector; for example... Figure 4 The diagram shows constant stator flux linkage curves with values ​​of {0.1, 0.15, 0.2, 0.25, 0.3, 0.35} for the stator flux linkage vector. The constant slip curves indicate multiple different Id-Iq combinations corresponding to the same slip, such as... Figure 4 The diagram shows constant slip curves with slip values ​​of {-10, -20, -30, ..., -70, -80, -90, -100}. The MTPA curves show several different Id-Iq combinations corresponding to the maximum torque-current ratio.

[0070] based on Figure 4 The intersection of the constant torque curve and the constant slip curve in the graph can determine that any given torque corresponds to multiple slips. The direct-axis current value Id and quadrature-axis current value Iq corresponding to each slip can enable the asynchronous motor to reach the given torque. Therefore, the slip set corresponding to the given torque can be determined based on the intersection of the constant torque curve and the multiple constant slip curves.

[0071] In the process of controlling the asynchronous motor based on a given torque, in response to the asynchronous motor's current amplitude exceeding a preset threshold and the inverter current flowing through the asynchronous motor being DC current, the controller can select a target slip from the slip set corresponding to the given torque. The sum of the target slip and the motor's electrical angular velocity is not zero. Control is performed using this target slip, thereby ensuring that the asynchronous motor can still achieve the given torque and that the inverter current flowing through the asynchronous motor is AC current. The preset threshold can be specifically set according to the actual application scenario; this embodiment does not impose any restrictions on this, for example, the preset threshold could be 50A. Figure 4 In the IdIq plane shown, the iso-slip curve of any slip in the slip set corresponding to a given torque intersects with the iso-torque curve of that given torque.

[0072] In one example, please refer to Figure 4For example, given a torque of -72 Nm, the controller controls the asynchronous motor based on the MTPA (Maximum Torque Per Ampere) curve. The asynchronous motor is currently operating at point A with a current slip of -10 rad / s. If the electric angular velocity of the asynchronous motor is also 10 rad / s, the sum of the current slip and the electric angular velocity is 0. The current flowing through the inverter of the asynchronous motor is DC current. The switching devices in the inverter need to withstand the excessive heat caused by the DC current. Therefore, the controller can select a target slip from the slip set corresponding to the given torque of -72 Nm. The sum of the target slip and the electric angular velocity of the motor is not 0. For example, if the selected target slip is -20 rad / s, and the electric angular velocity of the asynchronous motor is also 10 rad / s, the sum of the two is not 0. That is, the asynchronous motor can operate at point B while still achieving the given torque of -72 Nm, thereby protecting the switching devices in the inverter.

[0073] After selecting the target slip, the controller can determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the target slip and the given torque; then, based on the current expected values ​​of the direct-axis current and the current expected value of the quadrature-axis current, it controls the rotation of the asynchronous motor. The process of controlling the rotation of the asynchronous motor based on the current expected values ​​of the direct-axis current and the current expected value of the quadrature-axis current can be found in [reference needed]. Figure 2 The description of the embodiments will not be repeated here.

[0074] The process of determining the current expected value of the direct-axis current and the current expected value of the quadrature-axis current is illustrated here:

[0075] In the first possible implementation, please refer to Figure 5 The controller can perform PI regulation based on the difference between the target slip and the current slip of the asynchronous motor to obtain the target stator flux linkage vector; then, based on the target stator flux linkage vector and the given torque, it determines the current expected values ​​of the direct-axis current and the current expected values ​​of the quadrature-axis current. PI regulation is a linear control method. It uses the control deviation between the given value and the actual output value, and combines the proportional and integral of the deviation linearly to form the control quantity, thereby controlling the controlled object. PI regulation can proportionally respond to system deviations; once a deviation occurs, proportional regulation immediately exerts an adjustment effect to reduce the deviation.

[0076] For example, the controller can obtain the equal stator flux linkage curve corresponding to the target stator flux linkage vector (see [link to relevant documentation]). Figure 4 ) and the isotorque curve corresponding to the given torque (see Figure 4The constant stator flux linkage curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same target stator flux linkage vector; the constant torque curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same given torque; then, based on the intersection of the constant stator flux linkage curve and the constant torque curve, the current expected value of the direct-axis current and the current expected value of the quadrature-axis current are determined; furthermore, it can be carried out according to... Figure 2 The control process mentioned in the embodiment uses the current expected value of the direct-axis current and the current expected value of the quadrature-axis current to perform vector control on the asynchronous motor. Specifically, in... Figure 5 In this context, u1 represents the given torque, and u2 represents the target stator flux linkage vector.

[0077] In a second possible implementation, for example, it can be based on Figure 4 The embodiments mention equal slip curves for different slips and equal stator flux linkage curves for different stator flux linkage vectors, pre-calibrating the mapping relationship between different slips and stator flux linkage vectors. In practical applications, after selecting the target slip, the controller can obtain the target stator flux linkage vector based on the target slip and the pre-calibrated mapping relationship between different slips and stator flux linkage vectors; then, based on the target stator flux linkage vector and the given torque, it determines the current expected value of the direct-axis current and the current expected value of the quadrature-axis current. For example, the controller can obtain the equal stator flux linkage curve corresponding to the target stator flux linkage vector (see [link to documentation]). Figure 4 ) and the isotorque curve corresponding to the given torque (see Figure 4 Then, based on the intersection of the constant stator flux linkage curve and the constant torque curve, determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current.

[0078] In a third possible implementation, after selecting the target slip, the controller can acquire the constant slip curve of the target slip and the constant torque curve corresponding to the given torque; the constant slip interval curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same target slip; the constant torque curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same given torque; then, based on the intersection of the constant slip curve and the constant torque curve, the current expected value of the direct-axis current and the current expected value of the quadrature-axis current are determined; and then, according to... Figure 2 The control process mentioned in the embodiment uses the current expected value of the direct-axis current and the current expected value of the quadrature-axis current to perform vector control on the asynchronous motor.

[0079] In one exemplary embodiment, please refer to Figure 6 , Figure 6 A flowchart illustrating another control method for an asynchronous motor is shown. The method can be executed by a controller and includes:

[0080] In step S201, it is detected whether the current amplitude of the asynchronous motor is greater than a preset threshold and whether the current flowing through the inverter of the asynchronous motor is a direct current. If yes, proceed to step S202; otherwise, proceed to step S203.

[0081] In step S202, a target slip is selected from the slip set corresponding to the given torque, wherein the sum of the target slip and the electric angular velocity of the motor is not zero; based on the target slip and the given torque, the current expected value of the direct-axis current and the current expected value of the quadrature-axis current are determined.

[0082] In step S203, based on the given torque and the pre-calibrated MTPA curve, the expected values ​​of the current direct-axis current and the current quadrature-axis current under the condition of satisfying the maximum torque-current ratio are determined.

[0083] In step S204, the asynchronous motor is controlled to rotate according to the current expected value of the direct axis current and the current expected value of the quadrature axis current.

[0084] In this embodiment, if the current amplitude of the asynchronous motor is greater than a preset threshold and the current flowing through the inverter of the asynchronous motor is a DC current, the target slip can be reselected to protect the switching devices of the inverter; when the above situation does not occur, the asynchronous motor is controlled by MTPA (maximum torque-current ratio) so that the asynchronous motor can generate the maximum torque with the minimum current, and the energy consumption is minimized.

[0085] It is easy to understand that the solutions described in the above embodiments can be combined when there is no conflict, and not all of them will be listed in this disclosure.

[0086] Accordingly, please refer to Figure 1 This application also provides a control system for an asynchronous motor, including a controller 10, an inverter 20, and an asynchronous motor 30.

[0087] The controller 10 is configured to respond to the current amplitude of the asynchronous motor being greater than a preset threshold and the current flowing through the inverter of the asynchronous motor being a DC current, select a target slip from the slip set corresponding to a given torque, wherein the sum of the target slip and the electric angular velocity of the motor is not zero; determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the target slip and the given torque; and send a switching signal to the inverter 20 based on the current expected value of the direct-axis current and the current expected value of the quadrature-axis current.

[0088] The inverter 20 is used to output three-phase line voltage according to the switching signal to drive the asynchronous motor 30 to rotate.

[0089] In some embodiments, the current amplitude of the asynchronous motor is determined based on the previous expected value of the direct-axis current and the previous expected value of the quadrature-axis current of the asynchronous motor; or the current amplitude of the asynchronous motor is determined based on the observed value of the direct-axis current and the observed value of the quadrature-axis current of the asynchronous motor.

[0090] In some embodiments, the controller 10 is further configured to obtain the current slip and electrical angular velocity of the asynchronous motor; if the sum of the current slip and electrical angular velocity of the asynchronous motor is close to 0, the current flowing through the inverter of the asynchronous motor is determined to be a DC current.

[0091] In some embodiments, the controller 10 is specifically configured to perform PI adjustment based on the difference between the target slip and the current slip of the asynchronous motor to obtain a target stator flux linkage vector; and determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the target stator flux linkage vector and the given torque.

[0092] In some embodiments, the controller 10 is specifically configured to obtain the target stator flux vector based on the target slip and the pre-calibrated mapping relationship between different slips and stator flux vectors; and to determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the target stator flux vector and the given torque.

[0093] In some embodiments, the controller 10 is specifically configured to acquire the equal stator flux linkage curve corresponding to the target stator flux linkage vector and the equal torque curve corresponding to the given torque; the equal stator flux linkage curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same target stator flux linkage vector, and the equal torque curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same given torque; and determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the intersection of the equal stator flux linkage curve and the equal torque curve.

[0094] In some embodiments, the controller 10 is specifically configured to acquire the constant slip curve of the target slip and the constant torque curve corresponding to the given torque; the constant slip curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same target slip; the constant torque curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same given torque; and determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the intersection of the constant slip curve and the constant torque curve.

[0095] The implementation process of the controller's functions and roles in the above system is detailed in the corresponding steps of the above method, and will not be repeated here.

[0096] Accordingly, this application also provides a vehicle including the control system of the aforementioned asynchronous motor.

[0097] For example, the asynchronous motor is used as a generator in a vehicle to supply power to all electrical devices in the vehicle and to charge the vehicle's battery. Accordingly, this application also provides a computer program product, including a computer program that, when executed by a processor, is used to implement the aforementioned control method.

[0098] In an exemplary embodiment, a non-transitory computer-readable storage medium including instructions is also provided, such as a memory including instructions that can be executed by a processor of the device to perform the described method. For example, the non-transitory computer-readable storage medium may be a ROM, random access memory (RAM), CD-ROM, magnetic tape, floppy disk, and optical data storage device, etc.

[0099] A non-transitory computer-readable storage medium that, when instructions in the storage medium are executed by a terminal's processor, enables the terminal to perform the methods described above.

[0100] The embodiments of the subject matter and functional operation described in this specification can be implemented in the following ways: digital electronic circuits, tangibly embodied computer software or firmware, computer hardware including the structures disclosed in this specification and their structural equivalents, or combinations thereof. Embodiments of the subject matter described in this specification can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions encoded on a tangible, non-transitory program carrier for execution by a data processing apparatus or for controlling the operation of a data processing apparatus. Alternatively or additionally, the program instructions may be encoded on artificially generated propagation signals, such as machine-generated electrical, optical, or electromagnetic signals, which are generated to encode information and transmit it to a suitable receiving device for execution by the data processing apparatus. The computer storage medium may be a machine-readable storage device, a machine-readable storage substrate, a random or serial access memory device, or combinations thereof.

[0101] The processing and logic flow described in this specification can be executed by one or more programmable computers that execute one or more computer programs to perform corresponding functions by operating on input data and generating output. The processing and logic flow can also be executed by dedicated logic circuitry—such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application-Specific Integrated Circuits), and the device can also be implemented as dedicated logic circuitry.

[0102] Suitable computers for executing computer programs include, for example, general-purpose and / or special-purpose microprocessors, or any other type of central processing unit. Typically, the central processing unit receives instructions and data from read-only memory and / or random access memory. The basic components of a computer include a central processing unit for implementing or executing instructions and one or more memory devices for storing instructions and data. Typically, a computer will also include one or more mass storage devices for storing data, such as disks, magneto-optical disks, or optical disks, or the computer will be operatively coupled to such mass storage devices to receive data from or transfer data to them, or both. However, a computer is not required to have such devices. Furthermore, a computer can be embedded in another device, such as a mobile phone, a personal digital assistant (PDA), a mobile audio or video player, a game console, a global positioning system (GPS) receiver, or a portable storage device such as a universal serial bus (USB) flash drive, to name a few.

[0103] Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, such as semiconductor memory devices (e.g., EPROM, EEPROM, and flash memory devices), magnetic disks (e.g., internal hard disks or removable disks), magneto-optical disks, and CD-ROM and DVD-ROM disks. Processors and memory may be supplemented by or incorporated into dedicated logic circuitry.

[0104] While this specification contains numerous specific implementation details, these should not be construed as limiting the scope of any invention or the scope of the claims, but rather are primarily intended to describe features of specific embodiments of a particular invention. Certain features described in the various embodiments herein may also be implemented in combination in a single embodiment. Conversely, various features described in a single embodiment may also be implemented separately in various embodiments or in any suitable sub-combination. Furthermore, while features may function in certain combinations as described above and even initially claimed in this way, one or more features from a claimed combination may be removed from that combination in some cases, and a claimed combination may refer to a sub-combination or a variation thereof.

[0105] Similarly, although the operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring these operations to be performed in the specific order shown or sequentially, or requiring all illustrated operations to be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system modules and components in the above embodiments should not be construed as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[0106] Thus, specific embodiments of the subject matter have been described. Other embodiments are within the scope of the appended claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve the desired result. Furthermore, the processes depicted in the drawings are not necessarily shown in a specific order or sequence to achieve the desired result. In some implementations, multitasking and parallel processing may be advantageous.

[0107] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A control method for an asynchronous motor, characterized in that, include: In response to the asynchronous motor's current amplitude being greater than a preset threshold and the inverter current flowing through the asynchronous motor being DC current, a target slip is selected from the slip set corresponding to a given torque, wherein the sum of the target slip and the motor's electric angular velocity is not 0. Based on the target slip and the given torque, determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current; The asynchronous motor is controlled to rotate based on the current expected value of the direct-axis current and the current expected value of the quadrature-axis current.

2. The method according to claim 1, characterized in that, The current amplitude of the asynchronous motor is determined based on the previous expected value of the direct-axis current and the previous expected value of the quadrature-axis current of the asynchronous motor; or The current amplitude of the asynchronous motor is determined based on the observed values ​​of the direct-axis current and the quadrature-axis current of the asynchronous motor.

3. The method according to claim 1, characterized in that, Also includes: Obtain the current slip and electrical angular velocity of the asynchronous motor; If the sum of the current slip and electrical angular velocity of the asynchronous motor is close to 0, the current flowing through the inverter of the asynchronous motor is determined to be a direct current.

4. The method according to claim 1, characterized in that, The step of determining the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the target slip and the given torque includes: PI adjustment is performed based on the difference between the target slip and the current slip of the asynchronous motor to obtain the target stator flux vector; Based on the target stator flux linkage vector and the given torque, determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current.

5. The method according to claim 1, characterized in that, The step of determining the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the target slip and the given torque includes: The target stator flux vector is obtained based on the target slip and the pre-calibrated mapping relationship between different slips and the stator flux vector. Based on the target stator flux linkage vector and the given torque, determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current.

6. The method according to claim 4 or 5, characterized in that, The step of determining the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the target stator flux linkage vector and the given torque includes: Obtain the constant stator flux linkage curve corresponding to the target stator flux linkage vector and the constant torque curve corresponding to the given torque; the constant stator flux linkage curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same target stator flux linkage vector, and the constant torque curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same given torque; Based on the intersection of the constant stator flux linkage curve and the constant torque curve, determine the current expected value of the direct axis current and the current expected value of the quadrature axis current.

7. The method according to claim 1, characterized in that, The step of determining the current expected value of the direct-axis current and the current expected value of the quadrature-axis current based on the target slip and the given torque includes: Obtain the constant slip curve for the target slip and the constant torque curve corresponding to the given torque; the constant slip curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same target slip; the constant torque curve indicates a combination of multiple different direct-axis current values ​​and quadrature-axis current values ​​corresponding to the same given torque; Based on the intersection of the constant slip curve and the constant torque curve, determine the current expected value of the direct-axis current and the current expected value of the quadrature-axis current.

8. A control system for an asynchronous motor, characterized in that, Includes controller, inverter, and asynchronous motor; The controller is configured to perform the method according to any one of claims 1 to 7; and to send a switching signal to the inverter according to the current expected value of the direct-axis current and the current expected value of the quadrature-axis current; The inverter is used to output three-phase line voltage according to the switching signal to drive the asynchronous motor to rotate.

9. A vehicle, characterized in that, The control system for the asynchronous motor as described in claim 8.

10. A computer-readable storage medium storing computer instructions thereon, characterized in that, When the computer instructions are executed by the processor, they implement the steps of the method according to any one of claims 1 to 7.

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