Rotational-speed control method and apparatus for alternating-current motor, and alternating-current motor and storage medium

Abstract

Provided in the present application are a rotational-speed control method and apparatus for an alternating-current motor, and an alternating-current motor and a storage medium. The method comprises: acquiring three-phase current values of an alternating-current motor; on the basis of the three-phase current values, determining a first compensation voltage value of an α axis of the alternating-current motor and a second compensation voltage value of a β axis thereof; acquiring a first command voltage value of the α axis of the alternating-current motor and a second command voltage value of the β axis thereof; determining a third command voltage value on the basis of the first compensation voltage value and the first command voltage value; determining a fourth command voltage value on the basis of the second compensation voltage value and the second command voltage value; and controlling the rotational speed of the alternating-current motor on the basis of the third command voltage value and the fourth command voltage value.

Description

AC motor speed control method and device, AC motor, and storage medium

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on September 18, 2023, with application number 202311207365.7 and invention name “Speed ​​control method and device for AC motor, AC motor, storage medium”, the entire contents of which are incorporated by reference in this application. Technical Field

[0002] The present application relates to motor control technology, and in particular to a speed control method and device for an AC motor, an AC motor, and a storage medium. Background Art

[0003] Domestic electric vehicles use AC motors to convert electrical energy into mechanical energy, and three-phase AC power is used as the input power source for the AC motors. Ideally, three-phase AC power is a standard sine wave with equal amplitude and frequency and a phase shift of 120°. However, in practice, even if the input voltage is a standard sine wave, the AC motor's phase current can shift due to factors such as the AC motor's flux, resolver position signal deviations, and control algorithms, generating a DC offset component. This component is not fixed and can vary between phases.

[0004] The DC bias component in the AC motor's phase current can cause severe heating of the motor, reduce system efficiency, and result in unstable output torque. Therefore, it is necessary to quickly compensate for the DC bias component of the AC motor. Technical issues

[0005] In view of this, the AC motor speed control method and device, AC motor, and storage medium provided in this application can quickly compensate for the DC bias component of the AC motor. Technical Solutions

[0006] According to one aspect of an embodiment of the present application, a method for controlling the speed of an AC motor is provided, comprising: obtaining three-phase current values ​​of the AC motor; determining a first compensation voltage value of the α-axis and a second compensation voltage value of the β-axis of the AC motor based on the three-phase current values; obtaining a first command voltage value of the α-axis and a second command voltage value of the β-axis of the AC motor; determining a third command voltage value based on the first compensation voltage value and the first command voltage value; determining a fourth command voltage value based on the second compensation voltage value and the second command voltage value; and controlling the speed of the AC motor based on the third command voltage value and the fourth command voltage value.

[0007] According to one aspect of an embodiment of the present application, a speed control device for an AC motor is provided, comprising: a first acquisition module configured to acquire three-phase current values ​​of the AC motor; a first determination module configured to determine a first compensation voltage value of the α-axis and a second compensation voltage value of the β-axis of the AC motor based on the three-phase current values; a second acquisition module configured to acquire a first instruction voltage value of the α-axis and a second instruction voltage value of the β-axis of the AC motor; a second determination module configured to determine a third instruction voltage value based on the first compensation voltage value and the first instruction voltage value; a third determination module configured to determine a fourth instruction voltage value based on the second compensation voltage value and the second instruction voltage value; and a control module configured to control the speed of the AC motor based on the third instruction voltage value and the fourth instruction voltage value.

[0008] According to one aspect of an embodiment of the present application, an AC motor is provided, comprising a memory and a processor, wherein the memory stores a computer program that can be run on the processor, and when the processor executes the program, the method described in the embodiment of the present application is implemented.

[0009] According to one aspect of an embodiment of the present application, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the method provided in the embodiment of the present application is implemented. Beneficial effects

[0010] In an embodiment of the present application, a speed control method for an AC motor is provided, which determines a first compensation voltage value on the α-axis and a second compensation voltage value on the β-axis based on the three-phase current value of the AC motor; directly compensates the first compensation voltage value to the first command voltage value of the α-axis, and directly compensates the second compensation voltage value to the second command voltage value of the β-axis. In this way, there is no need to convert the superposition value of the obtained voltage compensation value and the original command voltage value (that is, the command voltage value before the first command voltage value and the second command voltage value are converted) into the above-mentioned command voltage value through an inverter module, thereby improving the speed of signal processing, and further being able to complete the compensation of the DC bias component in the three-phase AC power before the AC motor speeds up.

[0011] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings herein are incorporated into and constitute a part of this specification. These drawings illustrate embodiments consistent with the present application and, together with the specification, serve to illustrate the technical solutions of the present application. Obviously, the drawings described below are merely some embodiments of the present application. Those skilled in the art can, without inventive effort, derive other drawings from these drawings.

[0013] The flowcharts shown in the accompanying drawings are for illustrative purposes only and do not necessarily include all contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may be decomposed, while others may be combined or partially combined. Therefore, the actual execution order may vary depending on the actual situation.

[0014] FIG1 is a schematic diagram of an implementation flow of a method for controlling the speed of an AC motor provided in an embodiment of the present application;

[0015] FIG2 is a schematic diagram of an implementation flow of a method for obtaining a three-phase AC current value provided in an embodiment of the present application;

[0016] FIG3 is a schematic diagram of the relationship between the α-axis, the β-axis, and the dq-axis provided in an embodiment of the present application;

[0017] FIG4 is a schematic diagram of an implementation flow of a method for identifying a DC bias component of a three-phase AC current according to an embodiment of the present application;

[0018] FIG5 is a schematic diagram of an implementation flow of a method for controlling the speed of an AC motor provided in an embodiment of the present application;

[0019] FIG6 is a schematic diagram of a flow chart of a method for compensating a DC bias component of a three-phase AC current and controlling an AC motor according to an embodiment of the present application;

[0020] FIG7 is a schematic diagram of an AC motor inverter provided in an embodiment of the present application;

[0021] FIG8 is a schematic diagram of an implementation flow of a method for controlling the speed of an AC motor provided in an embodiment of the present application;

[0022] FIG9 is a schematic structural diagram of a speed control device for an AC motor provided in an embodiment of the present application;

[0023] FIG10 is a schematic structural diagram of an electronic device provided in an embodiment of the present application. Modes for Carrying Out the Invention

[0024] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the specific technical solutions of the present application will be further described in detail below in conjunction with the drawings in the embodiments of the present application. The following embodiments are used to illustrate the present application but are not intended to limit the scope of the present application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein are for the purpose of describing the embodiments of this application only and are not intended to limit this application.

[0026] In the following description, references to “some embodiments,” “this embodiment,” “embodiments of the present application,” and examples, etc., describe a subset of all possible embodiments. However, it can be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict.

[0027] The descriptions such as "first, second, third" appearing in the embodiments of this application are only for illustration and distinction of the described objects. There is no order, nor does it indicate any special limitation on the number of devices in the embodiments of this application, and cannot constitute any limitation on the embodiments of this application.

[0028] The DC offset component can cause the AC motor's output torque to be unstable, which in turn can cause vibration in related devices or equipment, potentially causing vehicle jitter, which is more noticeable when the vehicle starts. Therefore, it is essential to compensate for the DC offset component in the AC motor's three-phase AC current.

[0029] In a related scheme, three-phase current is collected, and the collected three-phase current is filtered through a filtering circuit to obtain a DC bias component of the three-phase current value. The compensation voltage value corresponding to the DC bias component is calculated, and the obtained compensation voltage value is superimposed on the original instruction voltage value to obtain the final instruction value.

[0030] However, this solution will cause signal processing delays, so this solution is more suitable for compensating for the DC bias component after the vehicle speeds up, but cannot timely compensate for the DC bias component when the vehicle is at a low speed. In another related solution, the DC bias component appearing in the AC motor is suppressed by using a DC bias component suppression device, an AC motor controller, and an AC motor drive system. In this solution, the actual current value of each phase of the AC motor is collected in real time by a current acquisition module, and the DC bias component suppression module is used to identify the DC bias component in the actual current value of each phase of the AC motor based on the actual current value of each phase, and a voltage compensation value for suppressing the DC bias component is obtained. The control module suppresses the DC bias component appearing in the AC motor based on the voltage compensation value. After real-time analysis of the DC bias component in the AC motor phase current, the DC bias component appearing in the AC motor is suppressed in real time through an adaptive compensatory control method.

[0031] However, using this solution to process circuit signals can cause compensation delays. Therefore, this solution is more suitable for compensating the DC offset component after the vehicle speed increases, and it compensates later during low-speed starts. However, the jitter caused by AC motor torque fluctuations is more noticeable during actual vehicle start-up.

[0032] In another related scheme, a method for removing the DC bias voltage during the AC current sampling process is provided. The AC current is sent to an analog circuit processing module, and is converted into an AC voltage signal superimposed with a DC bias voltage through a current sensor and a bias voltage circuit. The AC current is then converted into a discrete AC signal with a DC bias through an A / D module. Subsequently, a DC discrete signal representing the magnitude of the DC bias voltage and an AC discrete signal representing the magnitude and frequency of the AC current are obtained through a subtractor, an integrator, and a proportional amplifier, thereby achieving the removal of the DC bias voltage during the AC current sampling process.

[0033] However, since this method calculates the DC bias voltage through a processor, the signal processing speed is slow, and it does not involve AC motor control methods, especially low-speed and high-torque conditions. Therefore, this method cannot solve the DC bias compensation problem when the AC motor starts at low speed.

[0034] In summary, the main disadvantages of using a circuit module or processor to compensate for the DC bias component in an AC signal are as follows:

[0035] (1) The circuit used to compensate for the DC bias component of the three-phase AC current has a slow signal processing speed and is not suitable for compensating the DC bias component when the AC motor starts at a low speed.

[0036] (2) The DC bias voltage is calculated by the processor, the signal processing speed is slow, and the AC motor control method is not involved, especially the low-speed and high-torque working conditions.

[0037] Based on the above analysis, an embodiment of the present application provides a method for controlling the speed of an AC motor. The method is applied to a processor of the AC motor. FIG1 is a schematic diagram of an implementation flow of the method for controlling the speed of an AC motor provided in an embodiment of the present application. As shown in FIG1 , the method may include the following steps 101 to 106:

[0038] Step 101, obtaining the three-phase current value of the AC motor;

[0039] Step 102: determining a first compensation voltage value of an α-axis and a second compensation voltage value of a β-axis of the AC motor based on the three-phase current values;

[0040] Step 103, obtaining a first command voltage value of the α-axis and a second command voltage value of the β-axis of the AC motor;

[0041] Step 104: determining a third instruction voltage value according to the first compensation voltage value and the first instruction voltage value;

[0042] Step 105, determining a fourth instruction voltage value according to the second compensation voltage value and the second instruction voltage value;

[0043] Step 106: Control the speed of the AC motor according to the third command voltage value and the fourth command voltage value.

[0044] In an embodiment of the present application, a method for controlling the speed of an AC motor is provided. Based on the three-phase current values ​​of the AC motor, a first compensation voltage value on the α-axis and a second compensation voltage value on the β-axis are determined. The first compensation voltage value is directly applied to the first command voltage value on the α-axis, and the second compensation voltage value is directly applied to the second command voltage value on the β-axis. This eliminates the need to convert the superposition of the obtained voltage compensation value and the original command voltage value (i.e., the command voltage value before the conversion between the first command voltage value and the second command voltage value) into the command voltage value via an inverter module, thereby improving signal processing speed and enabling compensation for the DC offset component in the three-phase AC current before the AC motor accelerates. Furthermore, this method can also be applied to compensate for the DC offset component in the three-phase AC current during vehicle startup. This method can compensate for the DC offset of the AC motor before the vehicle stabilizes, stabilizing the vehicle's starting torque and reducing vehicle vibration.

[0045] The following describes further implementation methods and related terms of each of the above steps.

[0046] In step 101, the three-phase current values ​​of the AC motor are obtained.

[0047] In some embodiments, as shown in FIG2 , the processor may respectively collect the currents Iu and Iv of the AC motor through two current sensors, and then calculate the Iw of the AC motor based on the currents Iu and Iv. It is understood that Iu, Iv, and Iw are the three-phase current values ​​of the AC motor.

[0048] Of course, the processor can also obtain the Iu and Iv of the AC motor through other devices or equipment or circuits with current acquisition functions, thereby calculating the Iw of the AC motor. In the embodiment of the present application, the method for obtaining the current Iu and Iv of the AC motor is not limited.

[0049] In step 102 , a first compensation voltage value of an α-axis and a second compensation voltage value of a β-axis of the AC motor are determined based on the three-phase current values.

[0050] It should be noted that the relationship between the α-axis and the β-axis and the dq-axis is shown in Figure 3, where the α-axis is defined in the 0° direction, the β-axis is defined in the 90° direction, the d-axis is the rotor magnetic field direction of the AC motor, the q-axis is perpendicular to the rotor magnetic field direction, and the coordinate system where the dq-axis is located rotates synchronously with the rotor. The voltage on the α-axis is expressed as Vα, the voltage on the β-axis is expressed as Vβ, the current on the α-axis is expressed as iα, and the current on the β-axis is expressed as iβ.

[0051] In some embodiments, as shown in FIG4 , the processor may implement step 102 through steps 1021 and 1022 as follows:

[0052] Step 1021, determining a DC bias component of the three-phase current value;

[0053] Furthermore, in some embodiments, the processor may determine the DC bias component of the three-phase current value by setting a cutoff frequency of a low-pass filter according to a switching frequency of an insulated gate bipolar transistor (IGBT) when the AC motor starts; and performing low-pass filtering on the three-phase current values ​​respectively using the low-pass filter with the set cutoff frequency to obtain the DC bias component of the three-phase current value.

[0054] In the embodiment of the present application, the starting of the AC motor can also be understood as the starting of the related device or equipment (such as a vehicle) where the AC motor is located. That is, the starting of the AC motor can also be understood as the stage from the initial startup to the stable operation of the related device or equipment.

[0055] It should be noted that the starting speeds of AC motors in different brands of related equipment or devices (such as vehicles) vary, and different models of related equipment or devices from the same brand also have different starting speeds. Therefore, the corresponding IGBT switching frequencies of different related equipment or devices are also different. Furthermore, since noise signals are ubiquitous during current signal propagation, the acquired three-phase current values ​​contain not only DC bias components but also noise components. Therefore, setting an appropriate low-pass filter cutoff frequency based on the IGBT switching frequency at the start of the AC motor can adapt to different brands and models of related equipment or devices, while also filtering out noise components in the signal, thereby ensuring filtering effectiveness and improving the accuracy, reliability, and versatility of DC bias component compensation.

[0056] It should also be noted that in the embodiments of the present application, the low-pass filter is not limited and can be any type of low-pass filter, as long as it can obtain the DC bias components corresponding to the three-phase current values. For example, the low-pass filter can be a Butterworth filter or other types of low-pass filters.

[0057] Step 1022: Determine the first compensation voltage value and the second compensation voltage value based on the DC bias component of the three-phase current value.

[0058] Furthermore, in some embodiments, the processor may implement step 1022 as follows: using a regulator to convert the DC bias component of each phase current value into a corresponding compensation voltage value; and determining the first compensation voltage value and the second compensation voltage value based on the compensation voltage value of each phase of the three-phase current value.

[0059] In some embodiments, the processor may determine the first compensation voltage value and the second compensation voltage value by performing Clark transformation on the compensation voltage value of each phase of the three-phase current value to obtain the first compensation voltage value and the second compensation voltage value.

[0060] In step 103 , a first command voltage value of the α-axis and a second command voltage value of the β-axis of the AC motor are obtained.

[0061] In some embodiments, the processor may convert the three-phase current values ​​Iu, Iv, and Iw of the AC motor into the first command voltage value and the second command voltage value through Clark transformation. In one possible implementation, step 102 and step 103 are performed in parallel.

[0062] In step 104 , a third command voltage value is determined according to the first compensation voltage value and the first command voltage value.

[0063] In some embodiments, the processor may implement step 104 as follows: determining the third instruction voltage value according to the accumulated value of the first compensation voltage value and the first instruction voltage value;

[0064] The third command voltage value is equal to the accumulated value of the first compensation voltage value and the first command voltage value.

[0065] In step 105 , a fourth command voltage value is determined according to the second compensation voltage value and the second command voltage value.

[0066] In some embodiments, the processor may implement step 105 as follows: determining the fourth instruction voltage value according to the accumulated value of the second compensation voltage value and the second instruction voltage value;

[0067] The fourth command voltage value is equal to the accumulated value of the second compensation voltage value and the second command voltage value.

[0068] It should be noted that the processor superimposes the first compensation voltage value and the first instruction voltage value on the α axis, and superimposes the second compensation voltage value and the second instruction voltage value on the β axis. In one possible implementation, step 104 and step 105 are performed in parallel.

[0069] In step 106 , the rotational speed of the AC motor is controlled according to the third command voltage value and the fourth command voltage value.

[0070] In some embodiments, the processor may implement step 106 as follows: using a space vector pulse width modulation (SVPWM) control algorithm to convert the third instruction voltage value and the fourth instruction voltage value into a pulse width modulation (PWM) wave; and controlling the output current of the inverter through the PWM wave to control the speed of the AC motor.

[0071] It should be noted that the schematic diagram of the AC motor inverter is shown in Figure 7, where C represents a capacitor, u, v, and w represent sinusoidal AC electromotive forces with equal maximum values, the same frequency, and a phase difference of 120° in the AC motor, and u leads the v phase electromotive force by 120°, and v leads the w phase electromotive force by 120°, iu, iv, and iw represent the phase currents corresponding to u, v, and w, respectively, and Q1-Q6 are the six switches of the inverter. It can be understood that the PWM wave controls the switching action of the six switches Q1-Q6 of the inverter, thereby controlling the output current of the inverter to control the speed of the AC motor. The embodiment of the present application provides a method for controlling the speed of an AC motor. Figure 5 is a schematic diagram of the implementation flow of the method for controlling the speed of an AC motor provided by the embodiment of the present application. As shown in Figure 5, the method includes the following steps 501 to 512:

[0072] Step 501, setting the cutoff frequency of the low-pass filter according to the IGBT switching frequency when the AC motor starts;

[0073] Step 502: obtaining three-phase current values ​​of the AC motor according to the current sensor;

[0074] Step 503: The processor converts the three-phase current value of the AC motor into a first command voltage value of the α-axis and a second command voltage value of the β-axis through Clark transformation.

[0075] Step 504: low-pass filter the three-phase current values ​​respectively using a low-pass filter with a set cutoff frequency to obtain a DC bias component of the three-phase current values;

[0076] In a possible implementation, step 503 and step 504 are performed simultaneously. It can be understood that step 503 and steps 504-507 are two branches processed in parallel.

[0077] Step 505: The processor extracts the DC bias component of the three-phase current value and inputs it into the regulator;

[0078] Step 506 , the regulator converts the DC bias component of each phase current value into a corresponding compensation voltage value;

[0079] Step 507: The processor performs Clark transformation on the compensation voltage value of each phase of the three-phase current value to obtain a first compensation voltage value of the α-axis and a second compensation voltage value of the β-axis;

[0080] Step 508: The processor superimposes the first compensation voltage value and the first instruction voltage value to obtain a third instruction voltage value;

[0081] Step 509: The processor superimposes the second compensation voltage value and the second instruction voltage value to obtain a fourth instruction voltage value;

[0082] It should be noted that the processor superimposes the first compensation voltage value and the first instruction voltage value on the α axis, and superimposes the second compensation voltage value and the second instruction voltage value on the β axis. In one possible implementation, step 508 and step 509 are performed in parallel.

[0083] Step 510 , the processor inputs the third command voltage value and the fourth command voltage value into the SVPWM control algorithm;

[0084] Step 511: The processor converts the third instruction voltage value and the fourth instruction voltage value into a PWM wave using an SVPWM control algorithm;

[0085] In step 512 , the processor controls the output current of the inverter through a PWM wave to control the speed of the AC motor.

[0086] The following describes the application of the embodiment of the present application in a practical application scenario.

[0087] In an embodiment of the present application, a method for compensating a DC bias component of a three-phase AC current of an AC motor when an electric vehicle is starting (i.e., when the AC motor is starting) is provided. Under low-speed and high-torque vehicle conditions, a Butterworth filter or other filter is used to identify the DC bias component in the three-phase AC current. An AC compensation voltage corresponding to the DC bias component (i.e., the compensation voltage value for each phase of the three-phase current value) is then calculated. Compensation voltages for the α-axis and β-axis (i.e., a first compensation voltage value for the α-axis and a second compensation voltage value for the β-axis) are obtained based on a Clark transform. These voltages are then superimposed with control signals for the α-axis and β-axis (i.e., a first command voltage value for the α-axis and a second command voltage value for the β-axis). The inverter switches are controlled by SVPWM to complete AC motor control. This method achieves compensation for the DC bias component in the three-phase AC current before the vehicle speed increases. The method has the advantages of fast signal processing speed, high reliability, and strong versatility.

[0088] It should be noted that the relationship between the α-axis and the β-axis and the dq-axis is shown in Figure 3, where the α-axis is defined in the 0° direction, the β-axis is defined in the 90° direction, the d-axis is the rotor magnetic field direction of the AC motor, the q-axis is perpendicular to the rotor magnetic field direction, and the coordinate system where the dq-axis is located rotates synchronously with the rotor. The voltage on the α-axis is expressed as Vα, the voltage on the β-axis is expressed as Vβ, the current on the α-axis is expressed as iα, and the current on the β-axis is expressed as iβ.

[0089] The method for compensating the DC bias component of the three-phase AC current of the AC motor of the electric vehicle when starting is provided in the embodiment of the present application can be divided into a method for identifying the DC bias component of the three-phase AC current, a method for compensating the DC bias component, and an AC motor control method:

[0090] The schematic diagram of the method for identifying the DC bias component of the three-phase AC current is shown in FIG4 . The specific process is as follows:

[0091] (1) Set the appropriate low-pass filter cutoff frequency according to the IGBT switching frequency when the vehicle starts (i.e., when the AC motor starts);

[0092] (2) Obtain the three-phase current values ​​Iu, Iv, and Iw of the AC motor based on the current sensor;

[0093] (3) After the three-phase current values ​​pass through a low-pass filter (e.g., Butterworth filter), the DC bias components Iu-DC, Iv-DC, and Iw-DC are identified.

[0094] The method for identifying the DC bias component based on a low-pass filter is to set an appropriate low-pass filter cutoff frequency according to the IGBT switching frequency when the vehicle starts, thereby ensuring the filtering effect, filtering the three-phase currents Iu, Iv and Iw of the AC motor, and identifying the DC bias components Iu-DC, Iv-DC and Iw-DC therein.

[0095] The schematic diagram of the implementation of the DC bias component compensation of the three-phase AC current and the AC motor control method is shown in Figure 6. The specific process is as follows:

[0096] (1) The three-phase compensation voltages ΔUu, ΔUv, and ΔUw (i.e., the compensation voltage values ​​of each phase of the three-phase current values) corresponding to the DC bias components of the extracted three-phase current values ​​are calculated by the regulator;

[0097] (2) Clark transformation is performed on the compensation voltage values ​​ΔUu, ΔUv, and ΔUw of each phase of the three-phase current value to obtain the compensation voltage value ΔUα (i.e., the first compensation voltage value) of the α-axis and the compensation voltage value ΔUβ (i.e., the second compensation voltage value) of the β-axis of the AC motor;

[0098] (3) The compensation voltage value ΔUα is superimposed on the original instruction voltage value Uα (i.e., the first instruction voltage value) to obtain a new voltage instruction value Uα' (i.e., the third instruction voltage value); the compensation voltage ΔUβ is superimposed on the original instruction voltage value Uβ (i.e., the second instruction voltage value) to obtain a new voltage instruction value Uβ' (i.e., the fourth instruction voltage value);

[0099] (4) Uα' and Uβ' are used as inputs to the SVPWM control algorithm to obtain a PWM wave whose frequency and duty cycle meet the control requirements;

[0100] (5) PWM wave controls the operation of the six switching tubes of the inverter to realize the control of the AC motor (i.e., the speed control of the AC motor);

[0101] The schematic diagram of the AC motor inverter is shown in Figure 7, where C represents capacitance, u, v, and w represent sinusoidal AC electromotive forces in the AC motor with equal maximum values, the same frequency, and a phase difference of 120°. The u phase electromotive force leads the v phase electromotive force by 120°, and the v phase electromotive force leads the w phase electromotive force by 120°. iu, iv, and iw represent the phase currents corresponding to u, v, and w, respectively. Q1-Q6 are the six switches of the inverter. It can be understood that the PWM wave controls the switching actions of the six switches Q1-Q6 of the inverter, thereby realizing AC motor control.

[0102] Based on the DC bias component compensation method of α-axis and β-axis control, after extracting the DC bias component of the three-phase current value, the corresponding compensation voltage values ​​ΔUu, ΔUv, and ΔUw are calculated by the regulator. The compensation voltage values ​​are converted into the compensation voltage ΔUα of the α-axis and the compensation voltage ΔUβ of the β-axis of the AC motor through Clark transform. The compensation voltage ΔUα is superimposed on the original command voltage value Uα to obtain a new voltage command value Uα'. The compensation voltage ΔUβ is superimposed on the original command voltage value Uβ to obtain a new voltage command value Uβ'. The SVPWM control algorithm obtains a PWM wave with a frequency and duty cycle that meets the control requirements based on the voltage command value, controls the operation of the six switching tubes of the inverter, and realizes AC motor control.

[0103] The compensation principle of the DC bias component is shown in Figure 8. After the current sensor collects the three-phase current values ​​Iu, Iv, and Iw, the filter identifies the DC bias components Iu-DC, Iv-DC, and Iw-DC. Based on this, the corresponding three-phase compensation voltages ΔUu, ΔUv, and ΔUw are calculated. The compensation voltage ΔUα of the α-axis and the compensation voltage ΔUβ of the β-axis are obtained according to the Clark transform. These are then superimposed with the control signal Uα of the α-axis and the control signal Uβ of the β-axis to obtain Uα' and Uβ'. The SVPWM controls the operation of the inverter switches to complete the compensation of the DC bias component in the AC motor control.

[0104] A method for compensating the DC bias component of the three-phase AC current when a vehicle starts, under conditions where the vehicle's AC motor has low speed and high torque, identifies the DC bias component of the three-phase AC current value through a low-pass filter and forms a compensation voltage (i.e., the compensation voltage value of each phase of the three-phase current value) that is superimposed on the α-axis and β-axis. This method can compensate for the DC bias component in the three-phase AC current before the vehicle speed increases, has the advantages of fast signal processing speed, high reliability, and strong versatility, and helps stabilize the vehicle's starting torque and reduce vibration.

[0105] The above description is merely an implementation method provided in the embodiments of the present application. The protection scope of the embodiments of the present application is not limited to the above implementation methods. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed in the embodiments of the present application should be included in the protection scope recorded in the claims.

[0106] It should be noted that although the steps of the method of the present application are described in a specific order in the drawings, this does not require or imply that the steps must be performed in this specific order, or that all steps must be performed to achieve the desired results. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step, and / or one step may be decomposed into multiple steps; or steps in different embodiments may be combined to form a new technical solution.

[0107] Based on the foregoing embodiments, an embodiment of the present application provides a speed control device for an AC motor, which includes the modules included and the units included in each module, and can be implemented by a processor; of course, it can also be implemented by a specific logic circuit; in the implementation process, the processor can be an AI acceleration engine (such as NPU, etc.), GPU, central processing unit (CPU), microprocessor (MPU), digital signal processor (DSP) or field programmable gate array (FPGA), etc.

[0108] FIG9 is a schematic diagram of the structure of a speed control device for an AC motor provided in an embodiment of the present application. As shown in FIG9 , the device 90 includes a first acquisition module 901, a first determination module 902, a second acquisition module 903, a second determination module 904, a third determination module 905, and a control module 906; wherein:

[0109] A first acquisition module 901 is configured to acquire three-phase current values ​​of the AC motor;

[0110] A first determining module 902 is configured to determine a first compensation voltage value of an α-axis and a second compensation voltage value of a β-axis of the AC motor based on the three-phase current values;

[0111] A second acquisition module 903 is configured to acquire a first command voltage value of the α-axis and a second command voltage value of the β-axis of the AC motor;

[0112] A second determining module 904 is configured to determine a third command voltage value according to the first compensation voltage value and the first command voltage value;

[0113] a third determining module 905 configured to determine a fourth command voltage value according to the second compensation voltage value and the second command voltage value;

[0114] The control module 906 is configured to control the speed of the AC motor according to the third command voltage value and the fourth command voltage value.

[0115] In some embodiments, the first determination module 902 is configured to: determine a DC bias component of the three-phase current value; and determine the first compensation voltage value and the second compensation voltage value based on the DC bias component of the three-phase current value.

[0116] Furthermore, in some embodiments, the first determination module 902 is configured to: set the cutoff frequency of the low-pass filter according to the IGBT switching frequency when the AC motor starts; use the low-pass filter with the set cutoff frequency to low-pass filter the three-phase current values ​​respectively to obtain the DC bias components of the three-phase current values.

[0117] In some embodiments, the first determination module 902 is configured to: use a regulator to convert the DC bias component of each phase current value into a corresponding compensation voltage value; and determine the first compensation voltage value and the second compensation voltage value based on the compensation voltage value of each phase of the three-phase current value.

[0118] Furthermore, in some embodiments, the first determining module 902 is configured to perform Clark transformation on the compensation voltage value of each phase of the three-phase current value to obtain the first compensation voltage value and the second compensation voltage value.

[0119] In some embodiments, the second determining module 904 is configured to: determine the third command voltage value according to the accumulated value of the first compensation voltage value and the first command voltage value;

[0120] In some embodiments, the third determination module 905 is configured to determine the fourth instruction voltage value according to the accumulated value of the second compensation voltage value and the second instruction voltage value.

[0121] In some embodiments, the control module 906 is configured to: convert the third instruction voltage value and the fourth instruction voltage value into PWM waves using an SVPWM control algorithm; and control the output current of the inverter through the PWM waves to control the speed of the AC motor.

[0122] The description of the above device embodiment is similar to the description of the above method embodiment and has similar beneficial effects as the method embodiment. For technical details not disclosed in the device embodiment of this application, please refer to the description of the method embodiment of this application for understanding.

[0123] It should be noted that the division of modules in the embodiments of the present application is schematic and is merely a logical functional division. In actual implementation, other division methods may be used. Furthermore, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units. They may also be implemented in the form of a combination of software and hardware.

[0124] It should be noted that in the embodiments of the present application, if the above-mentioned method is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiments of the present application, or the part that contributes to the relevant technology, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a number of instructions for causing the AC motor to execute all or part of the methods described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a magnetic disk, or an optical disk. In this way, the embodiments of the present application are not limited to any specific combination of hardware and software.

[0125] An embodiment of the present application provides an AC motor. Figure 10 is a schematic diagram of the hardware entity of the electronic device of the embodiment of the present application. As shown in Figure 10, the electronic device 100 includes a memory 1001 and a processor 1002. The memory 1001 stores a computer program that can be run on the processor 1002. When the processor 1002 executes the program, the steps in the method provided in the above embodiment are implemented.

[0126] It should be noted that the memory 1001 is configured to store instructions and applications executable by the processor 1002, and can also cache data to be processed or processed by the processor 1002 and various modules in the AC motor 100 (for example, image data, audio data, voice communication data and video communication data), which can be implemented through flash memory (FLASH) or random access memory (RAM).

[0127] An embodiment of the present application provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the method provided in the above embodiment are implemented.

[0128] An embodiment of the present application provides a computer program product comprising instructions, which, when executed on a computer, enables the computer to execute the steps of the method provided in the above method embodiment.

[0129] It should be noted that the description of the above storage medium and device embodiments is similar to the description of the above method embodiments and has similar beneficial effects as the method embodiments. For technical details not disclosed in the storage medium, storage medium, and device embodiments of this application, please refer to the description of the method embodiments of this application for understanding.

[0130] It should be understood that "one embodiment" or "an embodiment" or "some embodiments" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, "in one embodiment" or "in an embodiment" or "in some embodiments" appearing throughout the specification do not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application. The above-mentioned serial numbers of the embodiments of the present application are for description only and do not represent the advantages and disadvantages of the embodiments. The above description of the various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced to each other. For the sake of brevity, they will not be repeated here.

[0131] The term "and / or" in this article is only a description of the association relationship between associated objects, indicating that there can be three relationships. For example, object A and / or object B can mean: object A exists alone, object A and object B exist at the same time, and object B exists alone.

[0132] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0133] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. The embodiments described above are merely illustrative. For example, the division of the modules is merely a logical function division. In actual implementation, there may be other division methods, such as: multiple modules or components can be combined, or can be integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the components shown or discussed can be through some interfaces, and the indirect coupling or communication connection of devices or modules can be electrical, mechanical or other forms.

[0134] The modules described above as separate components may or may not be physically separated, and the components displayed as modules may or may not be physical modules; they may be located in one place or distributed across multiple network units; some or all of the modules may be selected according to actual needs to achieve the purpose of this embodiment.

[0135] In addition, all functional modules in the embodiments of the present application can be integrated into one processing unit, or each module can be a separate unit, or two or more modules can be integrated into one unit; the above-mentioned integrated modules can be implemented in the form of hardware or in the form of hardware plus software functional units.

[0136] Those skilled in the art will understand that all or part of the steps of the above-mentioned method embodiment can be completed by hardware related to program instructions, and the aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps of the above-mentioned method embodiment; and the aforementioned storage medium includes: mobile storage devices, read-only memories (ROM), magnetic disks or optical disks, and other media that can store program codes.

[0137] Alternatively, if the above-mentioned integrated unit of the present application is implemented in the form of a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application, or the part that contributes to the relevant technology, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a number of instructions for causing the AC motor to execute all or part of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program code, such as mobile storage devices, ROMs, magnetic disks or optical disks.

[0138] The methods disclosed in the several method embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments.

[0139] The features disclosed in the several product embodiments provided in this application can be arbitrarily combined without conflict to obtain new product embodiments.

[0140] The features disclosed in the several method or device embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments or device embodiments.

[0141] The above is merely an embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for controlling the speed of an AC motor, wherein: The method comprises: Get the three-phase current value of the AC motor; Based on the three-phase current values, determining a first compensation voltage value of an α-axis and a second compensation voltage value of a β-axis of the AC motor; Acquire a first command voltage value of the α-axis and a second command voltage value of the β-axis of the AC motor; determining a third instruction voltage value according to the first compensation voltage value and the first instruction voltage value; determining a fourth instruction voltage value according to the second compensation voltage value and the second instruction voltage value; The rotation speed of the AC motor is controlled according to the third command voltage value and the fourth command voltage value.

2. The method according to claim 1, wherein: The determining, based on the three-phase current value, a first compensation voltage value of the α-axis and a second compensation voltage value of the β-axis of the AC motor comprises: Determining a DC bias component of the three-phase current value; The first compensation voltage value and the second compensation voltage value are determined based on the DC bias components of the three-phase current values.

3. The method according to claim 1 or 2, wherein: The step of determining the DC bias component of the three-phase current value comprises: According to the IGBT switching frequency when the AC motor starts, the cut-off frequency of the low-pass filter is set; The three-phase current values ​​are respectively subjected to low-pass filtering by using the low-pass filter with a set cut-off frequency to obtain direct current bias components of the three-phase current values.

4. The method according to claim 1 or 2, wherein: The determining the first compensation voltage value and the second compensation voltage value based on the DC bias component of the three-phase current value includes: The regulator is used to convert the DC bias component of each phase current value into a corresponding compensation voltage value; The first compensation voltage value and the second compensation voltage value are determined based on the compensation voltage value of each phase of the three-phase current value.

5. The method according to claim 4, wherein: The determining the first compensation voltage value and the second compensation voltage value based on the compensation voltage value of each phase of the three-phase current value includes: Clark transformation is performed on the compensation voltage value of each phase of the three-phase current value to obtain the first compensation voltage value and the second compensation voltage value.

6. The method according to any one of claims 1 to 5, wherein: The step of determining a third instruction voltage value according to the first compensation voltage value and the first instruction voltage value comprises: determining the third instruction voltage value according to the accumulated value of the first compensation voltage value and the first instruction voltage value; The step of determining a fourth instruction voltage value according to the second compensation voltage value and the second instruction voltage value comprises: The fourth command voltage value is determined according to an accumulated value of the second compensation voltage value and the second command voltage value.

7. The method according to any one of claims 1 to 6, wherein: The controlling the speed of the AC motor according to the third instruction voltage value and the fourth instruction voltage value comprises: Using an SVPWM control algorithm, converting the third instruction voltage value and the fourth instruction voltage value into a PWM wave; The output current of the inverter is controlled by the PWM wave to control the rotation speed of the AC motor.

8. A speed control device for an AC motor, wherein: The speed control device of the AC motor comprises: A first acquisition module is used to acquire the three-phase current value of the AC motor; A first determination module, configured to determine a first compensation voltage value of a shaft of the AC motor and a second compensation voltage value of a shaft based on the three-phase current value; A second acquisition module, used to acquire a first command voltage value of the α-axis and a second command voltage value of the β-axis of the AC motor; a second determining module, configured to determine a third instruction voltage value according to the first compensation voltage value and the first instruction voltage value; a third determining module, configured to determine a fourth instruction voltage value according to the second compensation voltage value and the second instruction voltage value; A control module is used to control the rotation speed of the AC motor according to the third instruction voltage value and the fourth instruction voltage value.

9. An AC motor, comprising a memory and a processor, wherein the memory stores a computer program that can be run on the processor, wherein: When the processor executes the program, the method according to any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, wherein: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

Images