Induction motor torque estimation method, system and device and storage medium

Abstract

The invention discloses an induction motor torque estimation method, system and device and a storage medium, and relates to the technical field of motors. The induction motor torque estimation method comprises the following steps: determining inductance parameters of a motor; acquiring operation parameters of the motor, and observing the component of the rotor flux linkage of the motor on the Q axis according to the inductance parameters, the operation parameters and a pre-constructed DQ-axis synchronous rotating coordinate system based on stator current vector orientation; and determining the motor torque according to the inductance parameter, the operation parameter and the component of the rotor flux linkage on the Q axis. According to the motor torque estimation method provided by the invention, the motor torque is estimated according to the component of the rotor flux linkage on the Q axis, the motor inductance parameter and the motor operation parameter, and motor body parameters such as resistance cannot be displayed in the estimation process, so that the method is not influenced by load and temperature rise change, and the estimation precision is high.

Description

Technical Field

[0001] The present application relates to the technical field of motors, and particularly to a method, system, device, and storage medium for estimating the torque of an induction motor. Background Art

[0002] Motor torque is an important indicator to describe the output performance of a motor. During the operation of the motor, it is usually necessary to obtain the real-time output torque of the motor to provide accurate torque feedback for functions such as torque closed-loop and active safety of the motor control system. Since torque sensors are expensive, in engineering, the torque of the motor is usually estimated online based on known signals that are easily obtained in the system. For example, a multi-dimensional look-up table method is used to estimate the torque by looking up a table according to the d-axis current feedback value and the q-axis current feedback value to obtain the actual torque feedback value of the motor. However, when conditions such as the load and temperature rise of the motor change, it will cause changes in the motor parameters, resulting in a decline in the performance of field-oriented control, causing deviations between the d-axis current feedback value and the q-axis current feedback value and the actual values, so that the torque obtained by looking up the table based on the current feedback value will deviate from the actual torque. Summary of the Invention

[0003] Object of the Invention: Embodiments of the present application provide a method, system, device, and storage medium for estimating the torque of an induction motor to improve the accuracy of motor torque estimation.

[0004] Technical Solution: A method for estimating the torque of an induction motor according to an embodiment of the present application includes:

[0005] Determine the inductance parameters of the motor;

[0006] Obtain the operating parameters of the motor, and determine the component of the rotor magnetic flux in the Q-axis according to the inductance parameters, the operating parameters, and a pre-constructed DQ-axis synchronous rotating coordinate system based on the stator current vector orientation;

[0007] Determine the motor torque according to the inductance parameters, the operating parameters, and the component of the rotor magnetic flux in the Q-axis.

[0008] In some embodiments, the operating parameters include electrical operating parameters and dynamic operating parameters;

[0009] The method for determining the component of the rotor magnetic flux in the Q-axis includes:

[0010] Establish a rotor magnetic flux observer according to the DQ-axis synchronous rotating coordinate system, the inductance parameters, the electrical operating parameters, and the dynamic operating parameters;

[0011] Determine the component of the rotor magnetic flux in the Q-axis according to the rotor magnetic flux observer.

[0012] In some embodiments, the electrical operating parameters include stator current and stator voltage;

[0013] A method for establishing a rotor flux observer includes:

[0014] Determine the component of the stator current on the D-axis according to the DQ-axis synchronous rotating coordinate system and the stator current;

[0015] Determine the component of the stator voltage on the Q-axis according to the DQ-axis synchronous rotating coordinate system, a pre-constructed αβ-axis two-phase stationary coordinate system, a pre-constructed dq-axis synchronous rotating coordinate system, the stator current, the stator voltage, the dynamic operating parameters, and a preset current loop;

[0016] Determine the rotor flux observer according to the DQ-axis synchronous rotating coordinate system, the inductance parameter, the component of the stator current on the D-axis, the component of the stator voltage on the Q-axis, and the dynamic operating parameters.

[0017] In some embodiments, the method for determining the component of the stator voltage on the Q-axis includes:

[0018] Determine the stator voltage and the angle between the stator voltage and the d-axis according to the preset current loop, the stator current, and the dq-axis synchronous rotating coordinate system;

[0019] Determine the angle between the stator current and the α-axis according to the stator current and the αβ-axis two-phase stationary coordinate system;

[0020] Determine the component of the stator voltage on the Q-axis according to the DQ-axis synchronous rotating coordinate system, the dynamic operating parameters, the stator voltage, the angle between the stator current and the α-axis, and the angle between the stator voltage and the d-axis.

[0021] In some embodiments, the dynamic operating parameters include one or more of synchronous frequency, rotor electrical angle, and slip.

[0022] In some embodiments, after establishing the rotor flux observer, it further includes:

[0023] Set the operating conditions of the rotor flux observer; the operating conditions include that the absolute value of the synchronous frequency is greater than a preset frequency.

[0024] In some embodiments, before determining the component of the rotor flux on the Q-axis according to the rotor flux observer, it further includes:

[0025] Perform a limiting operation on the rotor flux observer according to a preset limiting condition.

[0026] In some embodiments, the method for determining the motor torque includes:

[0027] Determine the motor torque according to the inductance parameter, the stator current, and the component of the rotor magnetic flux on the Q axis.

[0028] In some embodiments, after determining the motor torque, it further includes:

[0029] Determine the direction of the motor torque according to the positive or negative situation of the stator current, the component of the rotor magnetic flux on the Q axis, and a preset sign factor.

[0030] In some embodiments, the inductance parameter includes one or more of the excitation inductance, the rotor inductance, and the stator inductance;

[0031] A method for determining the inductance parameter includes:

[0032] Determine the stator inductance and the rotor inductance according to a preset current look-up table method;

[0033] Determine the excitation inductance according to the preset current look-up table method and a preset input current algorithm.

[0034] In some embodiments, the determining the excitation inductance according to the preset current look-up table method and the preset input current algorithm includes:

[0035] Determine the input current of the preset current look-up table method according to the preset input current algorithm;

[0036] Determine the rotor inductance of the motor according to the input current;

[0037] Determine the excitation inductance according to the d-axis current in the calibration data of the motor, the q-axis current in the calibration data, the measured torque, and the rotor inductance.

[0038] Correspondingly, an induction motor torque estimation system provided by an embodiment of the present application includes:

[0039] A first determination module for determining the inductance parameter of the motor;

[0040] An acquisition module for acquiring the operating parameters of the motor;

[0041] A second determination module for determining the component of the rotor magnetic flux of the motor on the Q axis according to the inductance parameter, the operating parameter, and a pre-constructed DQ-axis synchronous rotating coordinate system based on stator current vector orientation;

[0042] A third determination module for determining the motor torque according to the inductance parameter, the operating parameter, and the component of the rotor magnetic flux on the Q axis.

[0043] Correspondingly, an embodiment of the present application further provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the induction motor torque estimation method described above is implemented.

[0044] Correspondingly, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the induction motor torque estimation method described above is implemented.

[0045] Beneficial effects: Compared with the prior art, the induction motor torque estimation method, system, device, and storage medium according to the embodiments of the present application. The induction motor torque estimation method includes: determining the inductance parameters of the motor; obtaining the operating parameters of the motor, and determining the component of the rotor magnetic flux of the motor on the Q-axis according to the inductance parameters, operating parameters, and a pre-constructed DQ-axis synchronous rotating coordinate system based on the stator current vector orientation; determining the motor torque according to the inductance parameters, operating parameters, and the component of the rotor magnetic flux on the Q-axis. The motor torque estimation method provided by the present application estimates the motor torque based on the component of the rotor magnetic flux on the Q-axis, the motor inductance parameters, and the motor operating parameters. The resistance and other motor body parameters do not appear in the estimation process. Therefore, this method is not affected by load and temperature rise changes, and has high estimation accuracy. Description of the Drawings

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative efforts.

[0047] Figure 1 is a functional block diagram of an IM indirect vector control algorithm provided by an embodiment of the present application;

[0048] Figure 2 is a schematic diagram of the actual position and observed position of the rotor magnetic flux provided by an embodiment of the present application;

[0049] Figure 3 is another schematic diagram of the actual position and observed position of the rotor magnetic flux provided by an embodiment of the present application;

[0050] Figure 4 is a flowchart of an induction motor torque estimation method provided by an embodiment of the present application;

[0051] Figure 5 is a schematic diagram of three coordinate systems provided by an embodiment of the present application;

[0052] Figure 6It is a block diagram of an IM indirect vector control system with torque estimation provided in an embodiment of the present application;

[0053] Figure 7 It is a schematic diagram of torque direction judgment provided in an embodiment of the present application;

[0054] Figure 8 It is another schematic diagram of torque direction judgment provided in an embodiment of the present application;

[0055] Figure 9 It is another schematic diagram of torque direction judgment provided in an embodiment of the present application;

[0056] Figure 10 It is another schematic diagram of torque direction judgment provided in an embodiment of the present application;

[0057] Figure 11 It is an effect diagram of torque estimation under electric operating conditions provided in an embodiment of the present application;

[0058] Figure 12 It is an effect diagram of torque estimation under generating operating conditions provided in an embodiment of the present application;

[0059] Figure 13 It is a principle block diagram of an induction motor torque estimation system provided in an embodiment of the present application;

[0060] Figure 14 It is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application.

[0061] Reference numerals:

[0062] 101 - First determination module; 102 - Acquisition module; 103 - Second determination module; 104 - Third determination module; 100 - Induction motor torque estimation system. Detailed implementation manners

[0063] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0064] It should be understood that although terms such as first and second may be used herein to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Therefore, the first component described below may be referred to as the second component without departing from the teachings of the concept of the present application. As used herein, the term "and / or" includes any one of the associated listed items and all combinations of one or more of them.

[0065] Those skilled in the art can understand that the attached drawings are only schematic diagrams of exemplary embodiments and may not be to scale. The modules or processes in the attached drawings are not necessarily essential for implementing this application, and thus cannot be used to limit the protection scope of this application.

[0066] After research by the applicant, it is found that motor torque is an important indicator to describe the output performance of a motor. During the operation of the motor, it is usually necessary to obtain the real-time output torque of the motor to provide accurate torque feedback for functions such as torque closed-loop and active safety of the motor control system. Since torque sensors are expensive, the main estimation method used in engineering is to perform online estimation of motor torque based on known signals that are easily obtained in the system, and different types of motors will have different torque estimation methods according to their physical models and control principles. Induction motors are widely used in various industrial control fields due to their advantages such as simple structure, low cost, durability, and convenient maintenance. The torque estimation function for induction motor control systems is a key research point.

[0067] Induction motors (IMs) are widely used in various industrial control fields due to their advantages in terms of cost, reliability, and control performance. Currently, the main control method for IMs is to use field-oriented control (FOC) to complete the closed-loop control of torque and speed. Among them, the field-oriented control of IMs includes direct vector control and indirect vector control. Exemplarily, this application will be described by taking the IM indirect vector control system as an example.

[0068] Figure 1 is a functional block diagram implemented by an IM indirect vector control algorithm provided by an embodiment of this application. Please refer to Figure 1 , in the maximum torque per ampere (MTPA) / flux weakening function module of the IM field-oriented control system, it is necessary to determine the d-axis reference current and q-axis reference current according to the received required torque. Here, the method of looking up the MAP table is adopted. The real-time bus voltage, speed, and required torque are used as input information, and the reference current magnitude and current angle are obtained by looking up the table, and then the d-axis reference current and q-axis reference current are output through the calculation of the flux weakening module. Among them, the MAP table data is obtained by processing the calibration data of the motor against the dynamometer bench. The specific calibration method is to give the MTPA current command within the entire range of bus voltage and speed, and record information such as the measured torque of the bench. As Figure 1 shown, the scheme of the torque feedback module is to use the MAP table obtained by processing this calibration data, and then perform torque estimation in a table-lookup manner according to the d-axis current feedback value and q-axis current feedback value to obtain the actual torque feedback value of the motor

[0069] When the parameters of the induction motor body do not change, the look-up table method based on the calibrated data can achieve a high torque feedback accuracy. However, in actual applications, changes in conditions such as the load and temperature rise of the induction motor will cause changes in the motor parameters, resulting in a decline in the field-oriented control performance, deviations between the d-axis current feedback value, q-axis current feedback value and the actual values, and the torque obtained by looking up the table according to the current feedback value will deviate from the actual torque. Specifically as follows:

[0070] Using the look-up table method requires obtaining accurate d-axis current feedback values and q-axis current feedback values. However, during the actual operation of the motor, the observation of the rotor flux position is easily affected by changes in the motor parameters, resulting in orientation deviations. The d-axis current feedback value and q-axis current feedback value calculated based on the rotor flux position observation value will have errors compared with the true current value. In an indirect vector control system, regarding the slip ω s The calculation formula is:

[0071]

[0072] Among them, T r is the rotor time constant, R r is the rotor resistance, L r is the rotor inductance, i d 、i q respectively represent the d-axis current and q-axis current, and θ represents the current angle. The current value used for the calculation of the slip is the given current value, and the rotor time constant or the resistance-inductance parameter is the set value in the program. If this set value is consistent with the actual parameter value of the motor and the current loop control error is ignored, then the indirect FOC system based on this calculated slip value ω s can sense the rotor flux at the expected position, that is, the rotor flux position observation value calculated according to ω s is equal to the actual position, and the true values of the d-axis current, q-axis current, and current angle θ are the same as the given values. However, the temperature rise of the motor has a great influence on the rotor resistance. When the motor temperature rises, the actual rotor resistance value will become larger, but the set value is still used in the program to calculate the slip. Then, the d-axis current and current angle, q-axis current and current angle that can be achieved in the actual system based on this calculated slip value ω s are:

[0073]

[0074] In the formula, the symbols with * are all actual quantities. Ignoring the change in the rotor inductance and only considering that the actual rotor resistance value becomes larger, according to formula (2), it can be seen that the actual current angle θ * will be less than the given quantity θ, that is, the actual rotor flux position is ahead of the observation value, as Figure 2Schematic diagram of the actual position and observed position of the rotor flux linkage. In Figure 2 , is the actual rotor flux linkage. It can be seen from Figure 2 that when the temperature rise of the motor causes the rotor resistance value to be higher than the set value, compared with the actual d-axis current and q-axis current, the feedback value of the d-axis current is smaller, and the feedback value of the q-axis current is larger. When the motor temperature drops and the rotor resistance value is lower than the set value, as shown in Figure 3 Another schematic diagram of the actual position and observed position of the rotor flux linkage. Refer to Figure 3 , the feedback value of the d-axis current is larger, and the feedback value of the q-axis current is smaller. Therefore, depending on the feedback values of the d-axis current and q-axis current, they will be affected by the changes in motor parameters and cannot maintain a high torque feedback accuracy in complex and changing actual working conditions.

[0075] In view of this, the embodiments of the present application provide a method, system, device and storage medium for estimating the torque of a motor. The present application estimates the torque of the motor based on the component of the rotor flux linkage on the Q-axis, the motor inductance parameters and the motor operating parameters. The resistance and other motor body parameters will not appear in the estimation process. Therefore, this method is not affected by load and temperature rise changes and has high estimation accuracy.

[0076] Figure 4 is a flowchart of a method for estimating the torque of an induction motor provided in the embodiments of the present application. This method is applicable to the process of accurately estimating the torque of an induction motor in a motor control system. This method can be executed by a motor torque estimation system, which can be implemented in software and / or hardware, and this system can be configured in the processor or controller of the motor control system. Please refer to Figure 4 , this method includes the following steps:

[0077] Step 110: Determine the inductance parameters of the motor.

[0078] Among them, the accuracy of the inductance parameters of the motor will affect the accuracy of the subsequent component of the rotor flux linkage of the motor on the Q-axis and the accuracy of the motor torque estimation.

[0079] Among them, the inductance parameters include one or more of the excitation inductance, rotor inductance, stator inductance and total leakage inductance, and can be specifically set according to the actual situation, and no specific limitation is made here.

[0080] It should be noted that in the technical solution of the embodiments of the present application, the motor is taken as an induction motor as an example for illustration, and the same will not be repeated below.

[0081] Step 120: Obtain the operating parameters of the motor, and determine the component of the rotor flux linkage of the motor on the Q-axis according to the inductance parameters, operating parameters and a pre-constructed DQ-axis synchronous rotating coordinate system based on the stator current vector orientation.

[0082] Among them, the operating parameters of the motor include electrical operating parameters and dynamic operating parameters. Among them, the electrical operating parameters include at least one of stator current and rotor current. The dynamic operating parameters include one or more of synchronous frequency, rotor electrical angle, and slip.

[0083] In some embodiments, the method for determining the component of the rotor flux linkage on the Q axis specifically includes the following steps:

[0084] Step 1: Establish a rotor flux observer according to the DQ-axis synchronous rotating coordinate system, inductance parameters, electrical operating parameters, and dynamic operating parameters.

[0085] Figure 5 It is a schematic diagram of three coordinate systems provided in the embodiments of the present application. Please refer to Figure 5 , in the induction motor FOC control system, an αβ-axis two-phase stationary coordinate system, a dq-axis synchronous rotating coordinate system, and a DQ-axis synchronous rotating coordinate system are established. Among them, the rotor flux observer is established based on the DQ-axis synchronous rotating coordinate system oriented by the stator current vector.

[0086] In some embodiments, the method for establishing a rotor flux observer includes: determining the component of the stator current on the D axis according to the DQ-axis synchronous rotating coordinate system and the stator current; determining the component of the stator voltage on the Q axis according to the DQ-axis synchronous rotating coordinate system, the pre-established αβ-axis two-phase stationary coordinate system, the pre-established dq-axis synchronous rotating coordinate system, the stator current, the stator voltage, the dynamic operating parameters, and the preset current loop; determining the rotor flux observer according to the DQ-axis synchronous rotating coordinate system, the inductance parameters, the component of the stator current on the D axis, the component of the stator voltage on the Q axis, and the dynamic operating parameters.

[0087] Among them, the calculation formula of the rotor flux observer determined according to the DQ-axis synchronous rotating coordinate system, the inductance parameters, the component of the stator current on the D axis, the component of the stator voltage on the Q axis, and the dynamic operating parameters is:

[0088]

[0089] In formula (3), p is a differential operator; i sD is the component of the stator current on the D axis; ω e is the synchronous frequency; u sQ is the component of the stator voltage on the Q axis; ψ rD is the component of the rotor flux linkage on the D axis; ω s is the slip; ψ rQ is the component of the rotor flux linkage on the Q axis; L s is the stator inductance; L m is the excitation inductance; L ris the rotor inductance; σ is the leakage inductance coefficient.

[0090] Among them, the derivation process of the calculation formula (3) of the rotor flux observer is as follows:

[0091] Please refer to Figure 5 , and analyze based on the DQ-axis synchronous rotating coordinate system. Since the stator current vector I s falls entirely on the positive half-axis of the D-axis and the stator current on the Q-axis is 0, the voltage equations in the DQ coordinate system can be written as:

[0092]

[0093] In Equation (4), u sD is the component of the stator voltage on the D-axis, R s is the stator resistance, ψ sD is the component of the stator flux on the D-axis, ψ sQ is the component of the stator flux on the Q-axis, i sQ is the component of the stator current on the Q-axis, u rD is the component of the rotor voltage on the D-axis, R r is the rotor resistance, i rD is the component of the rotor current on the D-axis, u rQ is the component of the rotor voltage on the Q-axis, i rQ is the component of the rotor current on the Q-axis.

[0094] The flux linkage equation can be written as:

[0095]

[0096] In Equation (5), L s is the stator inductance; L m is the excitation inductance; L r is the rotor inductance. By combining the third equations in Equations (4) and (5) and dividing them after shifting the two equations, we can obtain:

[0097]

[0098] In Equation (6), T r is the rotor time constant, which is obtained by dividing L r by R r . By combining the fourth equations in Equations (4) and (5) and dividing them after shifting the two equations, we can obtain:

[0099]

[0100] Among them, the synchronous frequency and slip satisfy:

[0101] ω e = ωs +ω r (8);

[0102] In Equation (8), ω r is the electrical angular velocity of the rotor.

[0103] By combining the second equation in Equation (4), the fourth equation in Equation (4), and the fourth equation in Equation (5), and combining like terms, we can obtain:

[0104]

[0105] In Equation (9), σ is the leakage inductance coefficient. By combining Equations (6)-(9), eliminating the rotor time constant, and then solving for the differential terms of ψ rD and ψ rQ , the calculation formula (3) of the rotor flux observer can be obtained.

[0106] According to the calculation formula (3) of the rotor flux observer, the rotor flux observer formula does not contain the resistance parameter. Therefore, during the process of observing the two axial components ψ rD and ψ rQ of the rotor flux by integration, it will not be affected by the change of the resistance, thereby obtaining the relationship between the actual rotor flux and the stator current, overcoming the influence of the change of the rotor resistance parameter on the calculation of the rotor flux. Therefore, the motor torque estimation accuracy provided by the embodiments of the present application is high.

[0107] Referring to the calculation formula (3) of the rotor flux observer, it can be seen that the input quantities of the observer are mainly the synchronous frequency, the slip, the D-axis component of the stator current, and the Q-axis component of the stator voltage. Among them, the synchronous frequency, the slip, and the D-axis component of the stator current are all known quantities that can be directly obtained. For example, the synchronous frequency and the slip adopt the output quantities of the indirect vector control module. The D-axis component of the stator current is the stator current amplitude. The specific implementation process of the D-axis component of the stator current is as follows: Refer to Figure 5 , θ is represents the angle between the stator current I s and the α-axis; θ e represents the rotor flux position angle, that is, the electrical angle; θ represents the current angle. In the FOC system, the stator current vector I s can be calculated by Clark transformation based on the measured three-phase current, that is, the stator current magnitude and the position angle θ iS are known signals in the system. Therefore, according to the stator current and the DQ-axis synchronous rotating coordinate system, the D-axis component i sD of the stator current can be obtained.

[0108] Figure 6It is a block diagram of an IM indirect vector control system with torque estimation provided in an embodiment of the present application. Please refer to Figure 5 and Figure 6 , and the method for determining the component of the stator voltage on the Q axis specifically includes: determining the stator voltage and the included angle between the stator voltage and the d axis according to a preset current loop, stator current, and dq-axis synchronous rotating coordinate system; determining the included angle between the stator current and the α axis according to the stator current and the αβ-axis two-phase stationary coordinate system; determining the component of the stator voltage on the Q axis according to the DQ-axis synchronous rotating coordinate system, dynamic operating parameters, stator voltage, the included angle between the stator current and the α axis, and the included angle between the stator voltage and the d axis.

[0109] Among them, the calculation formula for the component of the stator voltage on the Q axis is:

[0110] u sQ =|U s |sin(θ us -θ is )=|U s |sin(θ udq +θ e -θ is ) (10);

[0111] In formula (10), |U s | represents the amplitude of the stator voltage vector, θ us represents the included angle between the stator voltage vector and the α axis, and θ udq represents the included angle between the stator voltage vector and the d axis.

[0112] Among them, the amplitude |U s | of the stator voltage vector and the included angle between the stator voltage and the d axis can be referred to Figure 6 , and the stator current of the motor is transformed from the abc three-phase stationary coordinate system to the αβ-axis two-phase stationary coordinate system through Clark transformation and Park transformation, and then transformed from the αβ-axis two-phase stationary coordinate system to the dq-axis synchronous rotating coordinate system to obtain the feedback current of the dq axis. Then, the feedback current of the dq axis and the given dq-axis current are adjusted through a preset current loop to output the amplitude |U s | of the stator voltage vector and the included angle between the stator voltage and the d axis.

[0113] In some embodiments, after establishing the rotor flux observer, it further includes: setting the operating conditions of the rotor flux observer; the operating conditions include that the absolute value of the synchronous frequency is greater than a preset frequency.

[0114] Among them, the specific value of the preset frequency can be set according to the actual situation and will not be specifically limited here.

[0115] Specifically, in order to avoid the adverse effects of the fluctuations of the rotor flux linkage, voltage, and current on the calculation of the rotor flux observer when the motor starts or operates at zero or low speeds, the operating conditions of the rotor flux observer need to be set as: the absolute value of the synchronous frequency |ω e | > the preset frequency ω e_min . Among them, the limit value of the preset frequency ω e_min is set to be less than the minimum value of the MTPA current angle to ensure that torque estimation can also be achieved under the locked-rotor condition.

[0116] It should be noted that when the operating conditions of the rotor flux observer are not met or the flux linkage observation value exceeds the limit value, a reset operation is performed.

[0117] Step 2: Determine the component of the rotor flux linkage on the Q-axis according to the rotor flux observer.

[0118] Specifically, according to the calculation formula of the rotor flux observer, after inputting the synchronous frequency, slip, the component of the stator current on the D-axis, and the component of the stator voltage on the Q-axis, the component of the rotor flux linkage on the Q-axis can be calculated.

[0119] In some embodiments, before determining the component of the rotor flux linkage on the Q-axis according to the rotor flux observer, it further includes: performing a limiting operation on the rotor flux observer according to the preset limiting conditions.

[0120] Specifically, referring to the calculation formula (3) of the rotor flux observer, it can be seen that there is a singularity where ψ rQ = 0. In order to avoid problems such as the rotor flux observer being unable to start or diverging and oscillating during operation, zero-crossing processing is required. For this purpose, the second formula in the calculation formula (3) of the rotor flux observer is written as:

[0121] pψ rD = m(ψ rD - L m i sD )(pψ rQ + ω s ψ rD ) + ω s ψ rQ (11);

[0122] In formula (11),

[0123] Before calculating the calculation formula (3) of the rotor flux observer in the program, first limit the value of m, and update the ψ rQ value according to the limited m value.

[0124] Thus, by the component ψ of the rotor flux linkage on the Q-axis rQPerform amplitude limiting, set the operating conditions of the rotor flux observer and the operation of resetting after exceeding the limit, which can avoid problems such as the rotor flux observer being unable to start or diverging and oscillating during operation, and ensure the normal operation of the rotor flux observer.

[0125] In addition, for the rotor flux observer provided in the embodiments of the present application, it can be adjusted according to the actual operating conditions. For example, if the system has low requirements for the dynamic response of motor torque estimation or is in a steady-state operation for most cases, the derivative of the rotor flux can be regarded as 0. For example, regarding pψ rD and pψ rQ as 0, then the rotor flux observer equation becomes:

[0126]

[0127] And set the operating conditions of the observer corresponding to Equation (12) as: the synchronous frequency and slip are not zero, and the rotor flux components can be solved as:

[0128]

[0129] After obtaining the absolute value of the component of the rotor flux on the Q-axis according to Equation (13), it is necessary to judge the operating conditions according to the direction of the synchronous frequency and slip, then judge the direction of the component of the rotor flux on the Q-axis according to the motor torque direction judgment method, and finally perform motor torque estimation. In addition, for the motor torque calculation method, the position angle of the rotor flux can be calculated according to the observed components of the rotor flux on the D-axis and Q-axis, the stator current on the actual d-axis and the stator current on the q-axis can be calculated according to this position angle, and finally the motor torque formula is used for torque calculation.

[0130] Step 130: Determine the motor torque according to the inductance parameters, operating parameters, and the component of the rotor flux on the Q-axis.

[0131] Among them, the inductance parameters include the excitation inductance and the rotor inductance. The operating parameters include the stator current.

[0132] Specifically, since the component of the rotor flux on the Q-axis is determined by the rotor flux observer, and the rotor flux observer provided in the present application does not explicitly contain the rotor resistance, the torque calculation process is not affected by the motor temperature rise and the change of the rotor resistance. Therefore, the motor torque estimated according to the component of the rotor flux on the Q-axis, the motor inductance parameters, and the motor operating parameters has high accuracy.

[0133] In some embodiments, the method for determining the motor torque includes: determining the motor torque according to the inductance parameters, the stator current, and the component of the rotor flux on the Q-axis.

[0134] Specifically, to reduce the introduction of observation errors, referring to the DQ-axis synchronous rotating coordinate system, the estimation formula for the motor torque is obtained based on the inductance parameters, operating parameters, and the component of the rotor magnetic flux on the Q-axis as follows:

[0135]

[0136] In formula (14), n p is the number of pole pairs.

[0137] Specifically, the signs of ψ rQ and the current angle θ in the torque estimation formula (14) are consistent, but the sign of ψ rQ calculated by the rotor magnetic flux observer is based on the DQ-axis synchronous rotating coordinate system.

[0138] It can be seen from this that the induction motor torque estimation method provided by the embodiments of the present application introduces a rotor magnetic flux observer in the stator current vector orientation coordinate system (i.e., the DQ-axis synchronous rotating coordinate system), utilizes the characteristic that this observer does not explicitly contain the rotor resistance, and estimates the motor torque based on the component of the rotor magnetic flux on the Q-axis, the motor inductance parameters, and the motor operating parameters, so that the torque calculation process is not affected by the motor temperature rise and the change of the rotor resistance, thereby ensuring the accuracy of the torque estimation. And the estimation method provided by the present application does not require additional hardware sensors, etc., and only uses the synchronous frequency, slip, stator current, and stator voltage to estimate the real-time motor torque, reducing the calculation amount and memory data of the controller compared with the look-up table method and improving the processing efficiency.

[0139] In some embodiments, after determining the motor torque, it further includes: determining the motor torque direction according to the positive and negative conditions of the stator current, the component of the rotor magnetic flux on the Q-axis, and a preset sign factor.

[0140] Specifically, in engineering, the positive direction of the motor torque is determined according to actual requirements, and the rotation directions of the coordinate systems based on the rotor magnetic flux observer and the FOC system are both positive in the counterclockwise direction. Therefore, it is necessary to specifically analyze the operating conditions of the stator voltage, current, magnetic flux vector, and torque in practice to judge the torque direction.

[0141] Figure 7 is a schematic diagram of a torque direction judgment provided in the embodiments of the present application, Figure 8 is another schematic diagram of a torque direction judgment provided in the embodiments of the present application, Figure 9 is another schematic diagram of a torque direction judgment provided in the embodiments of the present application, Figure 10 is another schematic diagram of a torque direction judgment provided in the embodiments of the present application. Figures 7 to 10For all distribution cases of stator voltage, current, and rotor flux linkage vectors under actual electric and power generation conditions, as well as four cases of the corresponding synchronous frequency rotation direction and torque direction, as shown in Table 1 specifically.

[0142] Table 1 Relationship Table between the Direction of the Q - axis Component of Rotor Flux Linkage and Torque Direction

[0143] Figure 7 <![CDATA[ψ rQ <0]]> <![CDATA[T e counterclockwise]]> Figure 8 <![CDATA[ψ rQ >0]]> <![CDATA[T e clockwise]]> Figure 9 <![CDATA[ψ rQ >0]]> <![CDATA[U e clockwise]]> Figure 10 <![CDATA[ψ rQ <0]]> <![CDATA[T e counterclockwise]]>

[0144] According to Table 1, it can be seen that there is a corresponding relationship between the direction of the component of the rotor flux linkage on the Q - axis and the torque direction. Therefore, the final torque estimation equation is proposed as:

[0145]

[0146] In Equation (15), a is a sign factor. When the positive torque direction is set to clockwise, a = 1 is set; when the positive torque direction is set to counterclockwise, a = - 1 is set.

[0147] In some embodiments, the method for determining inductance parameters includes: determining stator inductance and rotor inductance according to the preset current look - up table method; determining field inductance according to the preset current look - up table method and the preset input current algorithm.

[0148] Exemplarily, taking an induction motor as an example, during the operation of the induction motor, the inductance value changes with the change of stator current. Therefore, in this application, the preset current look - up table method is adopted to look up the inductance parameters according to the stator current for subsequent calculation of the rotor flux observer and torque.

[0149] Among them, the stator inductance and rotor inductance are determined according to the preset current look - up table method, and the specific implementation process is as follows: First, a set of stator inductance values need to be calibrated on the motor back - to - back test bench. The specific calibration method is to drag the induction motor to a relatively high speed n (such as 3000 RPM), issue a series of d - axis current values (range: 0 - Idmax) through the calibration mode, and keep the q - axis given current at 0 (corresponding slip is 0). Thus, each time a current command is issued, the bench data is recorded, and stator voltage and stator current data are obtained. Among them, the synchronous frequency of this process is consistent with the rotor electrical angular velocity, both being:

[0150]

[0151] When the speed is relatively high, the back - electromotive force generated by the rotation of the stator flux is much larger than the voltage of the stator resistance term. At this time, the stator resistance can be ignored, and thus the calculation formula for stator inductance is written as:

[0152]

[0153] After calibration, according to the bench data and Equation (17), the stator inductance L corresponding to each d-axis current is calculated s , and a set of MAP data is obtained. Thus, the inductance value can be obtained by looking up the table according to the current value through the one-dimensional table lookup method.

[0154] Since the values of the stator leakage inductance and the rotor leakage inductance are close, the rotor inductance can be regarded as equal to the stator inductance, that is, L r = L s . Thus, the stator inductance and the rotor inductance of the motor can be determined according to the preset current look-up table method.

[0155] Among them, the field inductance is determined according to the preset current look-up table method and the preset input current algorithm. The specific method includes: determining the input current of the preset current look-up table method according to the preset input current algorithm; determining the rotor inductance of the motor according to the input current; determining the field inductance according to the d-axis current in the calibration data of the motor, the q-axis current in the calibration data, the measured torque, and the rotor current.

[0156] Specifically, considering the influence of the d-axis and q-axis cross-coupling effects on the inductance during the operation of the motor, an input current algorithm is set. Among them, the calculation formula of the preset input current algorithm is:

[0157] i LUT = i d + ki q (18);

[0158] In Equation (18), the coefficient k represents the influence factor of the q-axis current on the inductance and needs to be set according to the actual system. i LUT represents the input current. According to i LUT and the MAP data for inductance look-up, the rotor inductance corresponding to the d-axis current and q-axis current can be obtained.

[0159] After having the method for obtaining the rotor inductance, it is necessary to calculate the field inductance L m according to the calibration data in torque control. In the calibration data record, each set of d-axis current and q-axis current corresponds to a measured torque, and the field inductance L m can be inversely deduced through the torque formula:

[0160]

[0161] In Equation (19), f(i LUT ) represents the look-up table function of the input current.

[0162] Among them, the total leakage inductance can be calculated according to the rotor inductance and the field inductance. The specific calculation formula is:

[0163] L σ = σL s≈2l rσ = 2(l r -l m ) (20);

[0164] It can be seen from this that by presetting the current look-up table method to adjust the inductance parameters online and considering the relationship between the inductance of the induction motor and the current, a preset current input algorithm is proposed. The preset current input algorithm is combined with the preset current look-up table method for calculating the look-up table input current, improving the accuracy of the inductance parameter calculation, and further improving the observation accuracy of the rotor flux observer to improve the estimation accuracy of the motor torque.

[0165] Figure 11 is a torque estimation effect diagram provided in the embodiment of the present application under the electric working condition, Figure 12 is a torque estimation effect diagram provided in the embodiment of the present application under the power generation working condition. Among them, the electric working condition refers to the situation where the motor obtains energy from the battery terminal and converts electrical energy into mechanical energy, and the power generation working condition refers to the situation where the motor converts mechanical energy into electrical energy and outputs it to the battery terminal. Exemplarily, please refer to Figure 11 and Figure 12 , and according to the torque estimation method provided by the present application, the torque distribution of a certain vehicle induction motor under the electric working condition and the power generation working condition is estimated, and the obtained torque estimation errors are respectively as Figure 11 and Figure 12 shown.

[0166] Figure 13 is a schematic structural diagram of the principle of an induction motor torque estimation system provided in the embodiment of the present application. Correspondingly, the embodiment of the present application also provides an induction motor torque estimation system. Please refer to Figure 13 , the induction motor torque estimation system 100 includes: a first determination module 101 for determining the inductance parameters of the motor; an acquisition module 102 for acquiring the operating parameters of the motor; a second determination module 103 for determining the component of the motor rotor flux in the Q-axis according to the inductance parameters, the operating parameters, and the pre-constructed DQ-axis synchronous rotating coordinate system based on the stator current vector orientation; a third determination module 104 for determining the motor torque according to the inductance parameters, the operating parameters, and the component of the rotor flux in the Q-axis.

[0167] The technical solution of the embodiment of the present application provides an induction motor torque estimation system. The motor torque estimation system includes a first determination module for determining the inductance parameters of the motor; an acquisition module for acquiring the operating parameters of the motor; a second determination module for determining the component of the rotor magnetic flux of the motor on the Q-axis according to the inductance parameters, the operating parameters, and a pre-constructed DQ-axis synchronous rotating coordinate system; and a third determination module for determining the motor torque according to the inductance parameters, the operating parameters, and the component of the rotor magnetic flux on the Q-axis. The motor torque estimation system provided by the present application estimates the motor torque based on the component of the rotor magnetic flux on the Q-axis, the motor inductance parameters, and the motor operating parameters. The resistance and other motor body parameters do not appear in the estimation process, so this method is not affected by load and temperature rise changes, and the estimation accuracy is high.

[0168] In some embodiments, the operating parameters include electrical operating parameters and dynamic operating parameters; the second determination module 103 is further configured to: establish a rotor magnetic flux observer according to the DQ-axis synchronous rotating coordinate system, the inductance parameters, the electrical operating parameters, and the dynamic operating parameters; and determine the component of the rotor magnetic flux on the Q-axis according to the rotor magnetic flux observer.

[0169] In some embodiments, the electrical operating parameters include stator current and stator voltage; the second determination module 103 is further configured to: determine the component of the stator current on the D-axis according to the DQ-axis synchronous rotating coordinate system and the stator current;

[0170] Determine the component of the stator voltage on the Q-axis according to the DQ-axis synchronous rotating coordinate system, a pre-constructed αβ-axis two-phase stationary coordinate system, a pre-constructed dq-axis synchronous rotating coordinate system, the stator current, the stator voltage, the dynamic operating parameters, and a preset current loop;

[0171] Determine the rotor magnetic flux observer according to the DQ-axis synchronous rotating coordinate system, the inductance parameters, the component of the stator current on the D-axis, the component of the stator voltage on the Q-axis, and the dynamic operating parameters.

[0172] In some embodiments, the second determination module 103 is further configured to: determine the stator voltage and the angle between the stator voltage and the d-axis according to the preset current loop, the stator current, and the dq-axis synchronous rotating coordinate system;

[0173] Determine the angle between the stator current and the α-axis according to the stator current and the αβ-axis two-phase stationary coordinate system;

[0174] Determine the component of the stator voltage on the Q-axis according to the DQ-axis synchronous rotating coordinate system, the dynamic operating parameters, the stator voltage, the angle between the stator current and the α-axis, and the angle between the stator voltage and the d-axis.

[0175] In some embodiments, the dynamic operating parameters include one or more of the synchronous frequency, the rotor electrical angle, and the slip.

[0176] In some embodiments, the motor torque estimation system 100 further includes an operating condition setting module for setting the operating conditions of the rotor flux observer; the operating conditions include that the absolute value of the synchronous frequency is greater than a preset frequency.

[0177] In some embodiments, the motor torque estimation system 100 further includes a limiting module for performing a limiting operation on the rotor flux observer according to preset limiting conditions.

[0178] In some embodiments, the third determination module 104 is configured to determine the motor torque according to the inductance parameter, the stator current, and the component of the rotor flux on the Q axis.

[0179] In some embodiments, the motor torque estimation system 100 further includes a torque direction determination module for determining the motor torque direction according to the positive and negative conditions of the stator current and the component of the rotor flux on the Q axis and a preset sign factor.

[0180] In some embodiments, the inductance parameter includes one or more of the excitation inductance, the rotor inductance, and the stator inductance; the first determination module 101 is configured to:

[0181] Determine the stator inductance and the rotor inductance according to a preset current look-up table method;

[0182] Determine the excitation inductance according to the preset current look-up table method and a preset input current algorithm.

[0183] In some embodiments, the first determination module 101 is further configured to: determine the input current of the preset current look-up table method according to the preset input current algorithm;

[0184] Determine the rotor inductance of the motor according to the input current;

[0185] Determine the excitation inductance according to the d-axis current in the calibration data of the motor, the q-axis current in the calibration data, the measured torque, and the rotor inductance.

[0186] Correspondingly, an embodiment of the present application further provides an electronic device. Please refer to Figure 14 , Figure 14 , which schematically shows the structural diagram of the electronic device according to the embodiment of the present application. The electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the above-mentioned induction motor torque estimation method are implemented. Since the above-mentioned motor torque estimation method has been described in detail, it will not be elaborated here.

[0187] Correspondingly, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned motor torque estimation method are implemented. Since the above-mentioned induction motor torque estimation method has been described in detail, it will not be elaborated here.

[0188] In the above embodiments, the descriptions of the respective embodiments have their own emphases. For parts not detailed in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0189] The above has introduced in detail the induction motor torque estimation method, system, device and storage medium provided by the embodiments of the present application, and specific examples have been used to elaborate the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the technical solution and its core idea of the present application; those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for estimating torque of an induction motor, characterized in that: include: Determine the inductance parameters of the motor; Acquire the operating parameters of the motor, and determine the component of the motor rotor flux on the Q axis according to the inductance parameter, the operating parameters, and a pre-constructed DQ axis synchronous rotating coordinate system based on stator current vector orientation; The motor torque is determined according to the inductance parameter, the operating parameter and the component of the rotor flux on the Q axis.

2. The induction motor torque estimation method according to claim 1, characterized in that: The operating parameters include electrical operating parameters and dynamic operating parameters; The method for determining the component of the rotor flux in the Q axis includes: Establishing a rotor flux observer according to the DQ-axis synchronous rotating coordinate system, the inductance parameter, the electrical operating parameter and the dynamic operating parameter; The component of the rotor flux on the Q axis is determined according to the rotor flux observer.

3. The induction motor torque estimation method according to claim 2, characterized in that: The electrical operating parameters include stator current and stator voltage; The method of establishing a rotor flux observer comprises: Determining a component of the stator current on the D axis according to the DQ axis synchronous rotating coordinate system and the stator current; Determine the component of the stator voltage on the Q axis according to the DQ axis synchronous rotating coordinate system, the pre-constructed αβ axis two-phase stationary coordinate system, the pre-constructed dq axis synchronous rotating coordinate system, the stator current, the stator voltage, the dynamic operating parameters and the preset current loop; The rotor flux observer is determined according to the DQ-axis synchronous rotating coordinate system, the inductance parameter, the component of the stator current on the D axis, the component of the stator voltage on the Q axis, and the dynamic operation parameter.

4. The method for estimating the torque of an induction motor according to claim 3, characterized in that: The method for determining the component of the stator voltage on the Q axis includes: Determine the stator voltage and the angle between the stator voltage and the d-axis according to the preset current loop, the stator current, and the dq-axis synchronous rotating coordinate system; Determining the angle between the stator current and the α-axis according to the stator current and the αβ-axis two-phase stationary coordinate system; The component of the stator voltage on the Q axis is determined according to the DQ axis synchronous rotating coordinate system, the dynamic operation parameters, the stator voltage, the angle between the stator current and the α axis, and the angle between the stator voltage and the d axis.

5. The method for estimating the torque of an induction motor according to claim 2, characterized in that: The dynamic operating parameters include one or more of a synchronous frequency, a rotor electrical angle and a slip.

6. The method for estimating the torque of an induction motor according to claim 5, characterized in that: After establishing the rotor flux observer, the method further includes: The operating condition of the rotor flux observer is set; the operating condition includes that the absolute value of the synchronous frequency is greater than a preset frequency.

7. The method for estimating the torque of an induction motor according to claim 2, characterized in that: Before determining the component of the rotor flux on the Q axis according to the rotor flux observer, the method further includes: The rotor flux observer is subjected to a limiting operation according to a preset limiting condition.

8. The method for estimating the torque of an induction motor according to claim 3, characterized in that: Methods for determining motor torque include: The motor torque is determined according to the inductance parameter, the stator current and the component of the rotor flux on the Q axis.

9. The method for estimating the torque of an induction motor according to claim 3, characterized in that: After determining the motor torque, the method further includes: The direction of the motor torque is determined according to the stator current, the positive and negative conditions of the component of the rotor flux on the Q axis, and a preset sign factor.

10. The method for estimating the torque of an induction motor according to claim 1, characterized in that: The inductance parameters include one or more of the excitation inductance, the rotor inductance and the stator inductance; Methods for determining inductance parameters include: Determine the stator inductance and the rotor inductance according to a preset current table lookup method; The excitation inductance is determined according to the preset current table lookup method and the preset input current algorithm.

11. The method for estimating the torque of an induction motor according to claim 10, characterized in that: The determining the excitation inductance according to the preset current table lookup method and the preset input current algorithm includes: Determine the input current of the preset current lookup table method according to the preset input current algorithm; determining the rotor inductance of the motor according to the input current; The excitation inductance is determined according to the d-axis current in the calibration data of the motor, the q-axis current in the calibration data, the measured torque, and the rotor inductance.

12. An induction motor torque estimation system, characterized in that: include: A first determination module, used to determine the inductance parameter of the motor; An acquisition module is used to acquire the operating parameters of the motor; A second determination module is used to determine the component of the motor rotor flux on the Q axis according to the inductance parameter, the operating parameter and a pre-constructed DQ axis synchronous rotating coordinate system based on the stator current vector orientation; The third determination module is used to determine the motor torque according to the inductance parameter, the operating parameter and the component of the rotor flux on the Q axis.

13. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the induction motor torque estimation method according to any one of claims 1 to 11 is implemented.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the induction motor torque estimation method according to any one of claims 1 to 11 is implemented.

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