Method and device for limiting q-axis current in MTPV region of asynchronous motor and motor control system
By generating a leakage flux coefficient mapping table for asynchronous motors and using a limiting control method, the current loop instability problem of asynchronous motors in the MTPV region was solved, and the torque control accuracy of the motor was improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LEADRIVE TECH (SHANGHAI) CO LTD
- Filing Date
- 2022-09-23
- Publication Date
- 2026-05-15
AI Technical Summary
In the MTPV region, the leakage flux coefficient of an asynchronous motor is affected by factors such as temperature and operating frequency, resulting in a large deviation between the q-axis current and the theoretical calculation value, which leads to current loop instability and poor torque control accuracy.
By pre-acquiring the MTPV curves of the asynchronous motor at different speeds, a leakage flux coefficient mapping table is generated. The target q-axis current is calculated by combining the target d-axis current and torque formulas, and amplitude limiting control is performed to ensure that the current matches the actual operating conditions.
It improves the accuracy of motor control, reduces q-axis current deviation caused by changes in temperature and operating conditions, stabilizes the current loop, and enhances torque control accuracy.
Smart Images
Figure CN115498940B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of motor control technology, and in particular to a method, device, and motor control system for limiting the q-axis current in the MTPV region of an asynchronous motor. Background Technology
[0002] With technological advancements, the development of new energy vehicles is accelerating, and the use of asynchronous motors as auxiliary drives is one of the main trends in future new energy vehicles. To maximize the output torque of the motor and achieve efficient operation, the maximum torque-voltage ratio (MTPV) control method is employed. When the motor switches from the constant power region to the MTPV region, it operates at a higher speed. Due to voltage limitations, maximizing the output torque requires that the ratio of the d-axis current to the q-axis current be consistent with the leakage flux coefficient. While the leakage flux coefficient is calculated using inductance, the actual coefficient is affected by factors such as motor temperature and operating frequency. Therefore, the actual leakage flux coefficient in the MTPV region has an error relative to the calculated value. Without control, this can lead to a significant difference between the achievable q-axis current and the theoretically calculated q-axis current, potentially causing current loop instability and poor torque control accuracy. Summary of the Invention
[0003] In order to overcome the above-mentioned technical defects, the purpose of this invention is to provide a method, device and motor control system for limiting the q-axis current in the MTPV zone of an asynchronous motor, which can solve the problem that the calculated q-axis current deviates significantly from the actual output q-axis current due to inaccurate inductance parameters, leading to current loop instability.
[0004] This invention discloses a method for limiting the q-axis current in the MTPV region of an asynchronous motor, comprising:
[0005] Obtain the MTPV curves of the asynchronous motor at different speeds, determine the leakage flux coefficients at different speeds and currents based on the MTPV curves, and generate a first mapping table.
[0006] A second mapping table is provided, which is used to provide the d-axis current of the asynchronous motor in the MTPV region at different speeds;
[0007] Obtain the target rotational speed and target torque, and obtain the target d-axis current through the second mapping table;
[0008] The target q-axis current is obtained by calculating based on the target torque and the target d-axis current according to the preset torque formula;
[0009] The target leakage flux coefficient is obtained from the first mapping table based on the target torque and the target d-axis current.
[0010] Preferably, the target q-axis current is limited based on the ratio of the target d-axis current to the target leakage flux coefficient. The limiting of the target q-axis current includes:
[0011] The ratio of the target d-axis current to the target leakage flux coefficient is set as the limit for the q-axis current;
[0012] If the target q-axis current exceeds the limit q-axis current, then the target q-axis current is controlled to the limit q-axis current.
[0013] Preferably, the preset torque formula is expressed as:
[0014]
[0015] Among them, T e For torque; i sd i is the d-axis current; sq L is the q-axis current; m For magnetizing inductance; n p L represents rotational speed. r This is the inductance of the motor rotor winding.
[0016] Preferably, offline or simulation calibration is used to generate MTPV curves of the asynchronous motor at different speeds.
[0017] Preferably, determining the leakage flux coefficient at different speeds and currents based on the MTPV curve includes:
[0018] For an asynchronous motor at any speed, obtain the ratio of the d-axis current to the q-axis current corresponding to different currents on the MTPV curve to generate the leakage flux coefficient under different currents.
[0019] The present invention also provides a current limiting device for the q-axis of an asynchronous motor in the MTPV region, comprising:
[0020] The first preprocessing module is used to obtain the MTPV curves of the asynchronous motor at different speeds, determine the leakage flux coefficients at different speeds and different currents based on the MTPV curves, and generate a first mapping table.
[0021] The second preprocessing module is used to provide a second mapping table, which is used to provide the d-axis current of the asynchronous motor in the MTPV region at different speeds;
[0022] The acquisition module is used to acquire the target rotational speed and target torque, and to acquire the target d-axis current through the second mapping table;
[0023] The calculation module is used to calculate the target q-axis current based on the target torque and the target d-axis current according to a preset torque formula;
[0024] The matching module is used to obtain the corresponding target leakage flux coefficient from the first mapping table based on the target d-axis current;
[0025] An execution module is used to limit the target q-axis current based on the ratio of the target d-axis current to the target leakage flux coefficient.
[0026] The present invention also provides a motor control system, including the above-described asynchronous motor MTPV zone q-axis current limiting device.
[0027] Compared with existing technologies, the above technical solution has the following advantages:
[0028] The present invention provides a method, device, and motor control system for limiting the q-axis current in the MTPV region of an asynchronous motor. The system is pre-calibrated offline or through simulation to obtain a first mapping table containing different leakage flux coefficients and a second mapping table for the d-axis current. After acquiring real-time motor parameters, including target speed, target torque, and target d-axis current, the target q-axis current is calculated according to a preset torque formula. The target leakage flux coefficient is matched from the first mapping table to limit the target q-axis current, resulting in a leakage flux coefficient with a high degree of matching with actual operating conditions. This reduces the possibility of discrepancies between the target q-axis current and the actual operating conditions due to temperature or operating conditions, and solves the problem of large deviations between the calculated q-axis current and the actual output q-axis current, which leads to current loop instability, thereby improving motor control accuracy. Attached Figure Description
[0029] Figure 1 This is a flowchart of Embodiment 1 of the asynchronous motor MTPV region q-axis current limiting method, device and motor control system described in this invention;
[0030] Figure 2 This is a schematic diagram of a module in Embodiment 2 of the asynchronous motor MTPV region q-axis current limiting method, device and motor control system described in this invention.
[0031] Figure label:
[0032] 7-Asynchronous motor MTPV zone q-axis current limiting device; 71-First preprocessing module; 72-Second preprocessing module; 73-Acquisition module; 74-Calculation module; 75-Matching module; 76-Execution module. Detailed Implementation
[0033] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.
[0034] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.
[0035] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.
[0036] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."
[0037] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0038] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.
[0039] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.
[0040] Example 1: This example discloses a method for limiting the q-axis current in the MTPV region of an asynchronous motor. (See attached document.) Figure 1 Including the following:
[0041] S100: Obtain the MTPV curve of the asynchronous motor at different speeds, determine the leakage flux coefficient at different speeds and different currents based on the MTPV curve, and generate the first mapping table;
[0042] Specifically, the motors used in this embodiment are all the aforementioned asynchronous motors used in new energy vehicles. In the above steps, offline or simulation calibration is performed in advance to generate MTPV curves of the asynchronous motor at different speeds. The MTPV curves include the changes in d-axis current and q-axis current at different speeds. The leakage flux coefficients corresponding to different speeds can be calculated based on the changes in d-axis current and q-axis current.
[0043] Specifically, determining the leakage flux coefficient at different speeds and currents based on the MTPV curve includes: for an asynchronous motor at any speed, obtaining the ratio of the d-axis current to the q-axis current corresponding to different currents on the MTPV curve to generate the leakage flux coefficient at different currents. Specifically, I d / I q =σ, where σ is the leakage flux coefficient, which is affected by factors such as the temperature and operating frequency of the asynchronous motor. In this embodiment, offline or simulation calibration is performed in advance, rather than based on the prior art. The calculation formula used in this method involves changes in temperature and inductance due to the increase in motor speed, leading to a deviation between the calculated result and the actual value. However, the corresponding σ obtained directly in the following steps of this implementation method is more accurate and has a higher consistency with the actual operating state. This allows for the calculation of the maximum permissible q-axis current under actual operating conditions, thereby achieving q-axis current limiting.
[0044] S200: Provides a second mapping table, which is used to provide the d-axis current of the asynchronous motor in the MTPV region at different speeds;
[0045] In the above steps, it should be noted that after entering the MTPV region, the d-axis will also undergo demagnetization in the motor control system, thus resulting in some changes in control compared to the MTPA region. In this embodiment, the second mapping table provides the d-axis current after entering the MTPV region, and I can be directly obtained by looking up the table. sd This method is convenient and efficient. Additionally, the second mapping table mentioned above can also be obtained through offline or simulation pre-calibration.
[0046] S300: Obtain the target rotational speed and target torque, and obtain the target d-axis current through the second mapping table;
[0047] In this embodiment, the target torque is directly acquired through control commands, while the target speed can be acquired through sensors. The I value corresponding to the motor's position at the target speed and target torque is obtained from a second mapping table. sd .
[0048] S400: Calculate the target q-axis current based on the target torque and the target d-axis current according to the preset torque formula;
[0049] Specifically, the preset torque formula is expressed as follows:
[0050]
[0051] Among them, T e For torque; i sd i is the d-axis current; sq L is the q-axis current; m For magnetizing inductance; n p L represents rotational speed. r This is the inductance of the motor rotor winding.
[0052] It should be noted that the above-mentioned preset torque formula is a general torque formula, and other parameters in this torque formula can be directly obtained from the asynchronous motor. sd If determined through the above step S300, the target q-axis current i can be calculated according to the formula. sq Based on the aforementioned known fact that the inductance changes with the increase of the asynchronous motor speed, this leads to a change in the calculated inductance of i. sq With the actual allowed i sq * There is an error, and the actual allowable maximum current i may be exceeded. sq * Therefore, based on this, it is necessary to obtain an accurate leakage flux coefficient σ, and then calculate an accurate value for i using this accurate σ. sq Restrictions should be imposed.
[0053] S500: Obtain the corresponding target leakage flux coefficient from the first mapping table based on the target torque and the target d-axis current;
[0054] Based on the MTPV curves of the asynchronous motor at different speeds obtained in S100 above, the corresponding target leakage flux coefficient can be directly obtained according to the target d-axis current, which is σ consistent with the actual working conditions, rather than the value that may have errors calculated by inductance in the prior art.
[0055] S600: Limit the target q-axis current based on the ratio of the target d-axis current to the target leakage flux coefficient.
[0056] In this embodiment, based on the above, in the MTPV region, I is satisfied.d / I q =σ, based on the above S300, obtain the accurate I d Based on the same number S400, the accurate σ can be obtained. At this point, the maximum allowable q-axis current i, consistent with the actual operating conditions, can be obtained according to the above formula. sq * And for the calculated i sq Limit the amplitude.
[0057] Specifically, limiting the target q-axis current includes:
[0058] The ratio of the target d-axis current to the target leakage flux coefficient is set as a limit for the q-axis current; when the target q-axis current exceeds the limit, the target q-axis current is controlled to the limit. In this embodiment, the limitation on the q-axis current mainly aims to reduce the error between the calculated value and the value under actual operating conditions, and to avoid the target q-axis current exceeding the limit due to the influence of temperature or operating conditions. sq * This addresses the issue of inaccurate inductance parameters causing a significant deviation between the calculated q-axis current and the actual output q-axis current, leading to current loop instability. This reduces the impact on torque control accuracy and also minimizes damage during motor control.
[0059] Example 2: The present invention also provides an asynchronous motor MTPV region q-axis current limiting device 7, see reference. Figure 2 ,include:
[0060] The first preprocessing module 71 is used to obtain the MTPV curves of the asynchronous motor at different speeds, determine the leakage flux coefficients at different speeds and different currents based on the MTPV curves, and generate a first mapping table.
[0061] Specifically, offline or simulation calibration is used in advance to generate MTPV curves of the asynchronous motor at different speeds. The leakage flux coefficients at different currents are generated by using the ratio of d-axis current to q-axis current at different speeds and different currents, which are used to form the first mapping table.
[0062] The second preprocessing module 72 is used to provide a second mapping table, which is used to provide the d-axis current of the asynchronous motor in the MTPV region at different speeds.
[0063] As can be seen, the second mapping table mentioned above provides the d-axis current after entering the MTPV region, which can be used for direct table lookup in the following acquisition module;
[0064] The acquisition module 73 is used to acquire the target rotational speed and target torque, and to acquire the target d-axis current through the second mapping table;
[0065] As a supplement, the acquisition module can also obtain other asynchronous motor-related parameters calculated according to the torque formula in the calculation module below, in order to obtain the target q-axis current.
[0066] Calculation module 74 is used to calculate the target q-axis current based on the target torque and the target d-axis current according to a preset torque formula;
[0067] The above-mentioned preset torque formula is a general torque formula as described in Embodiment 1. The target q-axis current is calculated after the target torque is directly obtained by the control module. However, the target q-axis current does not take into account the influence of motor temperature, working status, etc., so it may not match the actual working conditions.
[0068] Matching module 75 is used to obtain the corresponding target leakage flux coefficient from the first mapping table based on the target d-axis current;
[0069] In this embodiment, the leakage magnetic coefficient corresponding to the actual rotational speed and target d-axis current is obtained by looking up a pre-generated first mapping table, and the I value is satisfied based on MTPV. d / I q =σ, then I is consistent with the actual working conditions. sd σ obtains i sq * Based on this, the target q-axis current obtained from the above calculation module is limited.
[0070] The execution module 76 is used to limit the target q-axis current based on the ratio of the target d-axis current to the target leakage flux coefficient.
[0071] Specifically, using the calculated i that is consistent with the actual working conditions sq * As a limiting value, when the target q-axis current exceeds the limiting q-axis current i sq * Then, the target q-axis current is controlled to the limit q-axis current, thereby limiting the amplitude of the q-axis current.
[0072] In this embodiment, the first and second preprocessing modules are used for offline or simulation calibration to obtain a first mapping table containing leakage flux coefficients at different speeds and currents, and a second mapping table containing d-axis current. Then, the acquisition module acquires real-time motor parameters, including target speed, target torque, target d-axis current, and other parameters required by the calculation module. The calculation module calculates the target q-axis current using a preset torque formula based on the acquired parameters. Finally, the matching module obtains the target leakage flux coefficient from the first mapping table, and the final value is calculated based on I... sd σ obtains i sq * For the target q-axis current isq Amplitude limiting is applied. By setting up the matching module and the first preprocessing module, the leakage magnetic coefficient consistent with the actual operating conditions is obtained by looking up a table. The calculated target q-axis current is then limited to reduce the discrepancy between the target q-axis current and the actual operating conditions caused by temperature or operating conditions, thereby improving the torque control accuracy.
[0073] Example 3: This invention also provides a motor control system for new energy vehicles, including the asynchronous motor MTPV region q-axis current limiting device described in Example 2. Specifically, it also includes other modules or semiconductor elements for executing the motor controller, which will not be elaborated here. This system can be used to execute the asynchronous motor MTPV region q-axis current limiting method described in Example 1, reducing the large error between the achievable q-axis current and the theoretical current calculated from the torque due to changes in the leakage flux coefficient caused by factors such as motor temperature and operating frequency. This improves torque control accuracy and optimizes the asynchronous motor's operating state.
[0074] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.
Claims
1. A method for limiting the q-axis current in the MTPV region of an asynchronous motor, characterized in that, include: Obtain the MTPV curves of the asynchronous motor at different speeds, determine the leakage flux coefficients at different speeds and currents based on the MTPV curves, and generate a first mapping table. A second mapping table is provided, which is used to provide the d-axis current of the asynchronous motor in the MTPV region at different speeds. The second mapping table is obtained by offline or simulation pre-calibration. Obtain the target rotational speed and target torque, and obtain the target d-axis current through the second mapping table; The target q-axis current is obtained by calculating based on the target torque and the target d-axis current according to the preset torque formula; The target leakage flux coefficient is obtained from the first mapping table based on the target torque and the target d-axis current. The target q-axis current is limited based on the ratio of the target d-axis current to the target leakage flux coefficient; The limiting of the target q-axis current includes: The ratio of the target d-axis current to the target leakage flux coefficient is set as the limit for the q-axis current; When the target q-axis current exceeds the limited q-axis current, the target q-axis current is controlled to the limited q-axis current; the preset torque formula is expressed as: ； in, Torque; This refers to the d-axis current. This is the q-axis current; For magnetizing inductance; Rotational speed; The inductance of the motor rotor winding; Offline or simulation calibration is used to generate MTPV curves of the asynchronous motor at different speeds; The step of determining the leakage flux coefficient at different speeds and currents based on the MTPV curve includes: For an asynchronous motor at any speed, obtain the ratio of the d-axis current to the q-axis current corresponding to different currents on the MTPV curve to generate the leakage flux coefficient under different currents.
2. A current limiting device for the q-axis of an asynchronous motor in the MTPV region, characterized in that, include: The first preprocessing module is used to obtain the MTPV curves of the asynchronous motor at different speeds, determine the leakage flux coefficients at different speeds and different currents based on the MTPV curves, and generate a first mapping table. The second preprocessing module is used to provide a second mapping table, which is used to provide the d-axis current of the asynchronous motor in the MTPV region at different speeds. The second mapping table is obtained by offline or simulation pre-calibration. The acquisition module is used to acquire the target rotational speed and target torque, and to acquire the target d-axis current through the second mapping table; The calculation module is used to calculate the target q-axis current based on the target torque and the target d-axis current according to a preset torque formula; The matching module is used to obtain the corresponding target leakage flux coefficient from the first mapping table based on the target d-axis current; An execution module is used to limit the target q-axis current based on the ratio of the target d-axis current to the target leakage flux coefficient; The limiting of the target q-axis current includes: The ratio of the target d-axis current to the target leakage flux coefficient is set as the limit for the q-axis current; When the target q-axis current exceeds the limited q-axis current, the target q-axis current is controlled to the limited q-axis current; the preset torque formula is expressed as: ； in, Torque; This refers to the d-axis current. This is the q-axis current; For magnetizing inductance; Rotational speed; The inductance of the motor rotor winding; Offline or simulation calibration is used to generate MTPV curves of the asynchronous motor at different speeds; The step of determining the leakage flux coefficient at different speeds and currents based on the MTPV curve includes: For an asynchronous motor at any speed, obtain the ratio of the d-axis current to the q-axis current corresponding to different currents on the MTPV curve to generate the leakage flux coefficient under different currents.
3. A motor control system, characterized in that: Includes the asynchronous motor MTPV zone q-axis current limiting device as described in claim 2 above.