Method for stall heating protection of asynchronous motor, motor controller and motor control system

Abstract

This invention discloses a locked-rotor heating protection method, a motor controller, and a motor control system for an asynchronous motor. During locked-rotor heating, the winding phase sequence of current injection is periodically switched according to a preset commutation time interval and commutation sequence. Simultaneously, the injected d-axis current is controlled in stages during each commutation. This invention effectively alleviates problems such as phase current distribution imbalance, thermal stress concentration, and dynamic jitter, improving heating efficiency and safety.

Description

Technical Field

[0001] This invention belongs to the field of electric vehicle electric drive technology, specifically relating to a stall heating protection method for an asynchronous motor, a motor controller, and a motor control system. Background Technology

[0002] Under low-temperature operating conditions, the battery performance of electric vehicles degrades significantly, necessitating battery heating to maintain normal operation. Using a stalled rotor asynchronous motor for heating is a feasible battery method, but traditional stalled rotor heating strategies have some drawbacks.

[0003] On the one hand, traditional locked-rotor heating generally employs a static d-axis current injection strategy, which involves continuously applying a constant current at a fixed phase. This method results in the current being concentrated in a single-phase winding for an extended period, causing the copper conductor of that phase to overheat, while the temperatures of other phase windings remain relatively low, creating a temperature gradient. This uneven heat distribution not only subjectes the three-phase copper plates to repeated thermal expansion and contraction stresses, accelerating material fatigue and insulation layer deterioration, but may also trigger localized hot spots, increasing the risk of short circuits and threatening the structural integrity and operational safety of the motor.

[0004] On the other hand, during the current build-up process, if the d-axis current rises too quickly, the magnetic field orientation accuracy is difficult to maintain due to the time-varying nature of motor parameters or the response delay of the control loop. This results in a certain q-axis current component, which interacts with the rotor magnetic field to generate periodic pulsating torque. This torque is transmitted to the vehicle body through the transmission system, causing perceptible vehicle vibration. This not only reduces ride comfort but may also cause additional shocks and wear to the vehicle's transmission system and other components, affecting the vehicle's safety and durability.

[0005] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the aforementioned background technology and provide a stall heating protection method, motor controller, and motor control system for asynchronous motors, which can effectively alleviate phase current distribution imbalance, thermal stress concentration, and dynamic vibration problems, thereby improving heating efficiency and safety.

[0007] The technical solution adopted in this invention is: a method for protecting the stalled rotor heating of an asynchronous motor. During the stalled rotor heating process, the winding phase sequence of the current injection is periodically switched according to a preset commutation time interval and commutation sequence. At the same time, the injected d-axis current is controlled in a staged manner during each commutation.

[0008] Furthermore, the step of periodically switching the winding phase sequence of current injection according to a preset commutation time interval and commutation sequence includes: During the first phase of the stalled rotor heating process, current is injected into the first phase winding and the second phase winding; After the commutation interval, the second period begins, during which current is injected and switched to the second and third phase windings. After the commutation interval, the third period begins, during which current is injected and switched between the third phase winding and the first phase winding. The phase commutation operation is repeated in the first time period, the second time period, and the third time period until the heating stop condition is met.

[0009] Furthermore, the step of controlling the d-axis current injected in each cycle during each commutation in a staged manner includes: Gradual rise phase: After receiving the stall heating command, the d-axis current is controlled to rise from the initial value to the target value according to the preset first current change slope; Maintenance phase: After the d-axis current reaches the target value, the target value is maintained for a preset maintenance time; Rapid descent phase: When the heating stop condition is met, the d-axis current is reduced from the target value to the initial value according to the preset second current change slope; The slope of the first current change is less than the slope of the second current change.

[0010] Furthermore, during the gradual increase phase, the d-axis current increases linearly according to the following formula: Id = Id0 + ΔIup × t1; Where Id is the real-time d-axis current, Id0 is the initial value, ΔIup is the slope of the first current change, and t1 is the rise time of the d-axis current from the initial value to the target value.

[0011] Furthermore, during the rapid descent phase, the d-axis current decreases linearly according to the following formula: Id = Id1 - ΔIdown × t3; Where Id is the real-time d-axis current, Id1 is the target value, ΔIdown is the slope of the second current change, and t3 is the time it takes for the d-axis current to decrease from the target value to the initial value.

[0012] Furthermore, one or more of the commutation time interval, the first current change slope, the second current change slope, the holding time, and the target value can be adjusted according to the characteristics of the motor and the battery.

[0013] A motor controller is configured to perform the stall heating protection method for an asynchronous motor as described above.

[0014] An electric motor control system includes a motor controller as described above.

[0015] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the stall heating protection method for an asynchronous motor as described above.

[0016] A computer program product includes a computer program that, when executed, causes the stall heating protection method for an asynchronous motor as described above to be performed.

[0017] The beneficial effects of this invention are as follows: In the locked-rotor heating process, the present invention periodically switches the winding phase sequence of current injection according to a preset commutation time interval and commutation sequence. At the same time, the injected d-axis current is controlled in a staged manner during each commutation. By balancing the current distribution and finely controlling the current dynamic process, the present invention can effectively alleviate the imbalance of phase current distribution, thermal stress concentration and dynamic fluctuation, and improve heating efficiency and safety. Attached Figure Description

[0018] Figure 1 This is a timing diagram of the stall heating protection method of the present invention. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments to facilitate a clear understanding of the present invention, but these descriptions do not constitute a limitation on the present invention.

[0020] It should be understood that, when used in this application specification and the appended claims, the term includes indicating the presence of the described feature, integral, step, operation, element and / or component, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0021] Furthermore, references to one or more embodiments described in this application mean that one or more embodiments of this application include the specific features, structures, or characteristics described in connection with that embodiment. Therefore, statements appearing in different parts of this specification, such as in one embodiment, some embodiments, some other embodiments, and some still other embodiments, do not necessarily refer to the same embodiment, but rather mean one or more, but not all, embodiments, unless otherwise specifically emphasized.

[0022] like Figure 1 As shown, this application proposes a locked-rotor heating protection method for an asynchronous motor. During the locked-rotor heating process, the winding phase sequence of the current injection is periodically switched according to a preset commutation time interval and commutation sequence. At the same time, the injected d-axis current is controlled in a staged manner during each commutation.

[0023] For ease of understanding, the following explains some key terms in this embodiment: An asynchronous motor is an AC motor in which the rotor speed is lower than the speed of the rotating magnetic field of the stator. In electric vehicles, asynchronous motors are often used as drive motors.

[0024] The locked-rotor heating process refers to the process by which an asynchronous motor, when its rotor is locked or its speed is extremely low, heats up the battery or other components by injecting current into the stator windings and utilizing the internal losses of the motor.

[0025] The commutation time interval refers to the length of time elapsed between each switching when the phase sequence of the injected current windings is periodically changed. The setting of this time interval affects the distribution of current in different windings and the uniformity of heating. The time of each commutation can be recorded by a timer. When the timer reaches the commutation time interval, the motor controller issues a commutation command to switch the phase sequence of the injected current windings.

[0026] Commutation sequence refers to the arrangement of the windings that are injected with current in a preset order when the phase sequence of the current-injected windings is switched periodically.

[0027] The winding phase sequence refers to the arrangement order of the phase windings in the stator windings of an asynchronous motor, in which current is injected.

[0028] In vector control of asynchronous motors, the d-axis (direct axis) current component is typically used to establish a magnetic field, and its magnitude directly affects the motor's magnetic flux and the heat generated.

[0029] The phased control method refers to not using a single control strategy for the injection process of d-axis current, but using different current change rates or maintenance methods according to different stages of the heating process.

[0030] The start-up of the stall heating process in this application can be triggered by the vehicle control unit based on battery temperature, ambient temperature, or user commands. For example, when the battery temperature is below a preset threshold, the system automatically issues a stall heating command. Alternatively, the driver can manually activate the heating function through the in-vehicle human-machine interface.

[0031] During stalled rotor heating, the current injection winding phase sequence can be switched periodically. For example, it can be set to switch the current from the currently injected winding to the next winding at fixed time intervals. Specifically, current can be injected into the first phase winding first, then after a time interval, the current can be switched to the second phase winding, and after the same time interval, the current can be switched to the third phase winding, and so on. Alternatively, current can be injected into two phase windings simultaneously each time a switch occurs. For example, current can be injected into the first and second phase windings first, then after a time interval, the current can be switched to the second and third phase windings, and then the current can be switched to the third phase winding and the first phase winding, and so on. The commutation time interval can be a fixed value or dynamically adjusted according to the motor operating status or heating requirements. The commutation sequence can be preset to a fixed cyclic pattern.

[0032] During each commutation operation, the injected d-axis current can be controlled in stages. For example, at the start of stall heating, the d-axis current can be set to gradually increase from a lower initial value to a higher target value to avoid sudden current changes. After reaching the target value, the current can be maintained for a period of time to ensure continuous heating. When the heating process needs to be stopped, the d-axis current can be rapidly reduced to its initial value. This staged control method can divide the entire current injection process into two or more stages according to actual needs, with each stage employing a different current variation strategy. For example, it can be set to first increase at a slower rate, then maintain the current, and finally decrease at a slower rate.

[0033] This application achieves uniform current distribution across all phases by periodically switching the current injection phase sequence during stall heating, effectively preventing localized thermal stress concentration caused by excessive current in one phase and improving the temperature uniformity of each phase winding. Simultaneously, by employing staged control of the injected d-axis current, current changes are smoothly controlled, reducing the q-axis current component caused by excessively rapid current rise. This effectively suppresses vehicle vibration and improves the comfort and safety of electric vehicles during battery heating in low-temperature environments.

[0034] In one embodiment, this application further proposes the above-mentioned method for stall heating protection of asynchronous motor, wherein the step of periodically switching the winding phase sequence of current injection according to a preset commutation time interval and commutation sequence includes: During the first phase of the stalled rotor heating process, current is injected into the first phase winding and the second phase winding; After the commutation interval, the second period begins, during which current is injected and switched to the second and third phase windings. After the commutation interval, the third period begins, during which current is injected and switched between the third phase winding and the first phase winding. The phase commutation operation is repeated in the first time period, the second time period, and the third time period until the heating stop condition is met.

[0035] Specifically, periodically switching the current injection winding phase sequence refers to changing the combination of motor windings injected with current according to a preset pattern and time interval during stall heating. The purpose is to avoid a single winding being subjected to high current heating for an extended period, thereby balancing the temperature distribution of each phase winding, reducing localized thermal stress concentration, and extending the motor's service life. This switching can be performed using a pre-set fixed sequence, such as cyclically switching according to a specific phase sequence combination; alternatively, the switching sequence and timing can be dynamically adjusted through a control algorithm based on real-time monitoring of motor temperature, current distribution, and other parameters.

[0036] In the first phase of the stall-rotor heating process, injecting current into the first and second phase windings means that after the stall-rotor heating starts, any two phases of the motor's three-phase windings (e.g., phase A and phase B) are selected as the initial targets for current injection, and a timer is started. This operation is achieved by controlling the power switching devices (such as IGBTs or MOSFETs) in the motor driver, so that the current flows only through the selected two phase windings, thereby generating heat in these windings. In addition to selecting the first and second phase windings as the initial injection phases, the second and third phase windings, or the third and first phase windings, can also be selected as the initial injection phases, as long as the subsequent switching sequence can cover all winding combinations.

[0037] After the commutation interval, the second time period begins. Switching the current injection phase to the second and third phase windings means that after the first time period ends, and after a preset commutation interval (i.e., when the timer reaches T1), the control system switches the target windings for current injection from the first and second phase windings to the second and third phase windings. This commutation interval can be a fixed value, such as several milliseconds to tens of milliseconds, to ensure that the switching is completed in a sufficiently short time while avoiding excessive load on the control system due to excessively fast switching frequency; or it can be a variable that is dynamically adjusted according to factors such as motor operating status and temperature change rate.

[0038] After the commutation interval, the third period begins. Switching the current injection phase to the third phase winding and the first phase winding means that after the second period ends, and after the same commutation interval, the control system switches the target winding for current injection from the second and third phase windings to the third and first phase windings. This step completes the first cycle of the three-phase windings being combined in pairs, ensuring that all windings can participate in the current injection and heating process.

[0039] The commutation operation of the first, second, and third time periods is repeated until the heating stop condition is met. This means that the current injection phase sequence switching operation of the above three time periods will be continuously repeated, forming a continuous loop. This loop will continue until the preset heating stop condition is reached. The heating stop condition may include, but is not limited to: the battery temperature reaching the target value, the motor winding temperature reaching the upper limit, the heating time reaching the preset duration, or the vehicle system detecting other abnormal conditions that require stopping heating.

[0040] Through the above technical solution, this application clearly defines the specific steps and sequence of periodically switching the current injection phase sequence of the windings. For example, in the initial stage, current is injected into the A-phase and B-phase windings for heating. After a certain time T1, the current is switched to be injected into the B-phase and C-phase windings. After another time T1, the current is switched back to be injected into the C-phase and A-phase windings, and so on. This explicit phase-switching heating method avoids the problem of excessive current in one phase caused by a fixed angle. Because the current continuously switches between the three-phase windings, the current-bearing time of each phase winding is relatively uniform, thereby reducing the overheating phenomenon caused by a certain phase winding bearing a large current for a long time, effectively protecting the three-phase copper plates, and improving the service life and safety of the motor. At the same time, this regular cyclic switching ensures the continuity and uniformity of the heating process, improves heating efficiency, and thus ensures the normal operation of the battery and the reliability of the entire vehicle in low-temperature environments.

[0041] In one embodiment, this application further proposes to control the d-axis current injected in each cycle during each commutation in a phased manner (i.e., gradual rise and rapid fall), specifically including: a gradual rise phase, a maintenance phase, and a rapid fall phase.

[0042] During the gradual increase phase, upon receiving the stall heating command, the d-axis current is controlled to rise from its initial value to the target value according to a preset first current change slope. This gradual increase phase aims to smoothly increase the d-axis current and avoid sudden current changes. For example, the d-axis current can increase linearly to achieve a smoother current change. The first current change slope can be a fixed value preset based on the motor model, battery type, etc., or it can be adaptively adjusted based on dynamic parameters such as real-time motor temperature and battery state of charge. The initial value can be zero current or a preset minimum non-zero current value to avoid transient shocks that may occur during a start-up from zero. The target value can be a fixed preset value or it can be dynamically adjusted based on real-time feedback from battery temperature, motor winding temperature, ambient temperature, etc., to achieve more precise temperature control or efficiency optimization.

[0043] During the maintenance phase, after the d-axis current reaches the target value, it is maintained at the target value for a preset maintenance time t2. This maintenance phase aims to keep the d-axis current at the target value to provide stable heating power. The preset maintenance time t2 can be a fixed duration configured by the system or set by the user, or it can be calculated in real time by an algorithm based on parameters such as the difference between the current battery temperature and the target temperature, and the motor's thermal capacity, or it can be maintained until a certain condition (such as the battery temperature reaching a preset threshold or the motor winding temperature reaching its upper limit) is met.

[0044] During the rapid descent phase, when the heating stop condition is met, the d-axis current is reduced from the target value to the initial value according to a preset second current change slope. This rapid descent phase aims to quickly reduce the d-axis current to rapidly stop heating and reduce energy loss. For example, the d-axis current can decrease linearly to adapt to different stop conditions or system response requirements. The second current change slope can be a fixed value determined based on the system's requirements for heating stop response speed, motor inductance characteristics, etc., or it can be adaptively adjusted based on dynamic parameters such as the urgency of heating stop, remaining motor heat, and battery temperature.

[0045] This application further specifies that the slope of the first current change is less than the slope of the second current change. This means that during heating startup, the d-axis current rises steadily at a slower rate, while during heating shutdown, the d-axis current drops rapidly at a faster rate. This slope relationship can be set during system initialization through parameter configuration or enforced by control logic.

[0046] By employing the aforementioned phased d-axis current control scheme, particularly by setting the first current change slope to be smaller than the second current change slope, this application effectively addresses the problem of q-axis current component generation caused by improper current changes. During the gradual increase phase, the d-axis current rises slowly with a smaller first current change slope, allowing the motor's magnetic field to gradually establish, reducing the q-axis current component caused by magnetic field orientation deviation. This reduces motor torque fluctuations, prevents vehicle vibration, and improves ride comfort. During the maintenance phase, a stable d-axis current ensures continuous and effective heating. In the rapid decrease phase, the d-axis current drops rapidly with a larger second current change slope, enabling a quick response to heating stop commands, rapidly cutting off heating power, improving system response efficiency, and reducing unnecessary energy loss. This design ensures smooth heating start-up while also considering rapid heating stop, optimizing the dynamic current response during asynchronous motor stall heating, thereby improving the performance and reliability of electric vehicles in low-temperature environments.

[0047] In one embodiment, this application further proposes that during the gradual rise phase, the d-axis current rises linearly according to the following formula: Id = Id0 + ΔIup × t1; where Id is the real-time d-axis current, Id0 is the initial value, ΔIup is the first current change slope, and t1 is the rise time of the d-axis current from the initial value to the target value.

[0048] This formula defines the precise linear variation of the d-axis current during the gradual increase phase. Specifically, the motor controller can calculate and output the corresponding d-axis current command value according to this formula in each control cycle by executing a preset algorithm. This command value then drives the inverter through a pulse width modulation (PWM) signal, thereby controlling the actual current in the motor windings.

[0049] The real-time d-axis current refers to the d-axis current component actually injected into the motor windings by the control system at any given moment. This value is obtained by measuring the three-phase current of the motor in real time using a current sensor, and then decomposing it into d-axis and q-axis current components through coordinate transformations (such as Clark transformation and Park transformation). The initial value is the starting point of the d-axis current at the beginning of the gradual rise phase. Typically, this value can be set to 0A, indicating heating from a current-free state to ensure a smooth start-up process. In certain specific applications, a smaller non-zero value can be set to quickly achieve the heating effect or maintain a certain baseline state. The slope of the first current change determines the rate of increase of the d-axis current. This slope can be determined experimentally or through simulation based on factors such as motor model, battery characteristics, and ambient temperature, to obtain an optimal fixed value. For example, ΔIup can be set to 0.2A / ms and stored in the controller. The rise time t1 is the duration of the gradual rise phase. This time can be calculated using the formula t1=(Id1-Id0) / ΔIup based on the initial value Id0, the target value Id1, and the first current change slope ΔIup.

[0050] Through the above technical solution, the rise of the d-axis current during stall heating is precisely controlled to a linear change. This linear and predictable current rise effectively avoids magnetic field orientation deviations caused by excessively rapid or uneven current rise, thereby suppressing the generation of the q-axis current component. Since the q-axis current component is one of the main causes of vehicle vibration, precisely controlling the linear rise of the d-axis current can significantly reduce vehicle vibration during stall heating startup, improve ride comfort, and reduce impact and wear on the vehicle's transmission system and other components, thus enhancing vehicle safety and durability. Furthermore, this controlled current rise process provides a stable foundation for the subsequent maintenance and rapid descent phases, ensuring the stability and reliability of the entire stall heating protection method.

[0051] In one embodiment, this application further proposes that during the rapid descent phase, the d-axis current decreases linearly according to the following formula: Id = Id1 - ΔIdown × t3; where Id is the real-time d-axis current, Id1 is the target value, ΔIdown is the second current change slope, and t3 is the d-axis current decreasing from the target value to the initial value.

[0052] Specifically, this technical solution precisely controls the d-axis current's descent during the rapid descent phase by introducing a clear linear descent formula. Id1, the target value, refers to the initial value of the d-axis current at the start of the rapid descent phase, and also the current value maintained during the sustaining phase. This target value typically represents the maximum d-axis current during stall heating. Id1 can be pre-stored as a system parameter in the motor controller's non-volatile memory and loaded upon system startup; alternatively, it can be obtained by looking up a table or calculating in real-time based on the current battery temperature, motor temperature, or heating power requirements, enabling more flexible heating control. ΔIdown, the second current change slope, defines the rate at which the d-axis current decreases during the rapid descent phase. ΔIdown can be a preset fixed value, determined experimentally or through simulation to ensure a rapid current decrease while avoiding excessive surges, such as ΔIdown being set to 3A / ms; or it can be dynamically adjusted based on the motor's current operating state (e.g., temperature, speed), battery status, or system load. For example, a faster descent slope can be used when the motor temperature is high to stop heating more quickly. t3 refers to the time variable that starts timing from the beginning of the fast descent phase, and it reflects the duration of the current decrease process.

[0053] By introducing a linear descent formula (Id = Id1 - ΔIdown × t3) during the rapid descent phase, this application can precisely control the d-axis current descent trajectory. This formula ensures that the d-axis current smoothly and predictably descends from the target value Id1 to the initial value at a preset second current change slope ΔIdown. This linear and controlled descent avoids control instability and system oscillations that may be caused by sudden current changes or nonlinear variations. Therefore, when the motor stops heating, the changes in its magnetic field and torque will be more gradual, effectively suppressing vehicle vibration caused by rapid current changes and improving ride comfort. Simultaneously, precise current control also improves the reliability and consistency of the stall heating process, reduces impact and wear on the motor drive system and other components, and extends the vehicle's service life.

[0054] In one embodiment, this application further proposes that one or more of the above-mentioned commutation time interval T1, first current change slope ΔIup, second current change slope ΔIdown, holding time t2, and target value Id1 can be adjusted according to the characteristics of the motor and the battery.

[0055] Specifically, setting the commutation time interval is crucial for ensuring uniform heating of each phase winding. It can be preset to a fixed value, for example, based on the thermal time constant of the motor winding or an empirical value; or it can be dynamically adjusted according to the current operating status of the motor, temperature distribution, or the heating requirements of the battery. For example, by monitoring the temperature of each phase winding in real time and adjusting the commutation time interval according to the temperature difference, a more balanced heating effect can be achieved.

[0056] The setting of the first current change slope directly affects the smoothness of the current rise, and thus the impact on the system during heating startup. This first current change slope can be preset to a fixed value, for example, based on the response characteristics of the motor control system and the allowable level of vibration; or it can be adaptively adjusted based on the inertia of the motor rotor, the accuracy of the field-oriented control, or the instantaneous power handling capacity of the battery, to effectively suppress the q-axis current component caused by field-oriented deviation while ensuring rapid heating, thereby avoiding vehicle vibration. The second current change slope refers to the rate at which the d-axis current decreases from the target value to the initial value when the heating stop condition is met. The setting of this slope affects the smoothness of the current decrease at the end of heating, which is crucial for reducing system impact and wear. This second current change slope can be preset to a fixed value, for example, based on the stability of the motor control system and the mechanical strength of the transmission system; or it can be dynamically adjusted based on the actual state of the motor and battery, such as motor temperature, battery state of charge (SOC), or the system's requirements for smoothness, to ensure a smooth end to the heating process and avoid additional impact on the vehicle's transmission system.

[0057] The duration setting directly determines the total heating time and energy injection amount. This duration can be preset to a fixed value, for example, based on experience or expected heating effect; or it can be dynamically adjusted according to the current battery temperature, target heating temperature, ambient temperature, or real-time temperature of the motor windings to ensure that the battery reaches the required temperature while avoiding motor overheating.

[0058] The target value determines the heating power and heating rate. This target value can be preset to a fixed value, for example, based on the rated current of the motor windings, the maximum discharge power of the battery, or the maximum allowable temperature rise of the system; or it can be adaptively adjusted according to the battery's state of charge, state of health (SOH), ambient temperature, or the required heating rate to provide the best heating effect under different operating conditions.

[0059] The above technical solution allows for the adjustment of one or more parameters, including the commutation time interval, the first current change slope, the second current change slope, the holding time, and the target value, based on the characteristics of the motor and battery. This enhances the flexibility and adaptability of the asynchronous motor stall heating protection method. This adjustability enables the heating strategy to precisely match the actual needs of different motor models and batteries in different states, avoiding problems such as low heating efficiency, uneven temperature distribution, and inability to adapt to varying operating conditions that can result from fixed parameters. Specifically, optimizing the commutation time interval effectively balances the temperature of each phase winding, reducing local thermal stress; adjusting the first current change slope effectively suppresses the q-axis current component caused by magnetic field orientation deviation during heating startup, thus preventing vehicle vibration and improving ride comfort; adjusting the second current change slope ensures a smooth current drop at the end of heating, reducing system impact; and adjusting the holding time and target value allows for precise control of heating duration and power based on actual heating needs and battery status, achieving efficient and safe heating. Overall, this solution addresses thermal stress and vibration issues while further enhancing the intelligence and reliability of the stall heating protection method, ensuring that electric vehicles maintain excellent performance and safety even in low-temperature environments.

[0060] In one embodiment, this application provides a motor controller configured to perform a stall heating protection method for an asynchronous motor.

[0061] Specifically, configuring a motor controller to implement a stall protection method for an asynchronous motor means that the motor controller is specifically designed, programmed, or configured at the hardware, software, or firmware level to accurately implement the stall protection method for the asynchronous motor according to predetermined logic and algorithms. This configuration ensures that the controller possesses the computing power, storage capacity, and interface capabilities required to execute the method.

[0062] The above technical solution integrates the stall-rotor heating protection method for asynchronous motors into the motor controller, enabling the controller to act as a unified execution unit, precisely coordinating and managing the entire heating process. This controller seamlessly coordinates the periodic switching of winding phase sequence with the staged control of the d-axis current, ensuring that the d-axis current smoothly transitions at a preset slope during commutation, avoiding sudden current changes due to improper control. This precise control and coordination capability ensures uniform current distribution across the three-phase windings, improving temperature uniformity, reducing thermal stress concentration, and extending motor lifespan. Simultaneously, the controller's staged control of the d-axis current, especially the gradual rise phase, effectively suppresses the generation of the q-axis current component, avoiding transient q-axis current caused by magnetic field orientation deviation, thereby preventing vehicle vibration, improving ride comfort, and reducing impact and wear on the vehicle's transmission system. Overall, this configuration enables the stall-rotor heating protection method to be implemented reliably and efficiently, improving the reliability and safety of the motor in low-temperature environments.

[0063] In one embodiment, this application further proposes a motor control system for an electric vehicle, including a motor controller, sensors, and an asynchronous motor.

[0064] Meanwhile, the motor controller is the core electronic control unit in an electric vehicle, responsible for receiving control commands, executing control algorithms, and driving the motor. It typically consists of hardware components, such as a microcontroller, power module, and sensor interfaces, as well as software components, such as control strategies and fault diagnosis. The motor controller is configured to implement the aforementioned stall-rotor heating protection method for the asynchronous motor. Its function is to precisely control the current injection, phase sequence switching, and staged control of the d-axis current of the asynchronous motor to achieve efficient and safe stall-rotor heating. Sensors, including current sensors and temperature sensors, are used to monitor the motor's current, temperature, and other parameters in real time and feed this information back to the motor controller. The asynchronous motor is the actuator for implementing stall-rotor heating, and the heat it generates can be transferred to the battery for heating through a heat exchange device.

[0065] By integrating the asynchronous motor and motor controller into a single electric vehicle motor control system, the effective implementation of the stall heating protection method can be ensured. Specifically, the system utilizes the heat generated by the asynchronous motor in a stalled state to heat the battery. Simultaneously, the motor controller is configured to periodically switch the winding phase sequence of the injected current and control the d-axis current in stages. This integration optimizes the coordination of the entire heating process, enabling the motor controller to directly and precisely control the asynchronous motor in real time. Through commutation operations, the temperature of each phase winding can be balanced, effectively reducing localized thermal stress concentration, thereby extending the motor's lifespan and improving its safety. Furthermore, by controlling the injected d-axis current in stages during each commutation, particularly controlling the current rise slope during the gradual increase phase, excessive q-axis current components caused by magnetic field orientation deviations can be effectively avoided, thus suppressing vehicle vibration, improving ride comfort, and reducing impact and wear on the vehicle's transmission system and other components. Therefore, this motor control system can significantly improve the performance and reliability of electric vehicles in low-temperature environments, while ensuring the long-term stable operation of the motor and vehicle.

[0066] This application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps described in the above-described method embodiments.

[0067] This application provides a computer program product, including a computer program, which, when run on an electronic device, enables the electronic device to perform the steps described in the various method embodiments above.

[0068] In applications, the processor can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0069] In applications, memory can be an internal storage unit of an electronic device in some embodiments, such as a hard drive or RAM. In other embodiments, memory can be an external storage device of the electronic device, such as a plug-in hard drive, SmartMediaCard (SMC), Secure Digital (SD) card, or FlashCard. Furthermore, memory can include both internal and external storage units of the electronic device. Memory is used to store operating systems, applications, bootloaders, data, and other programs, such as program code for computer programs. Memory can also be used to temporarily store data that has been output or will be output.

[0070] Computer programs include computer program code, which can be in the form of source code, object code, executable files, or some intermediate form. Computer-readable media can include at least: any entity or device capable of carrying computer program code to an electronic device, recording media, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media. Examples include USB flash drives, portable hard drives, magnetic disks, or optical disks. In some jurisdictions, according to legislation and patent practice, computer-readable media cannot be electrical carrier signals or telecommunication signals.

[0071] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0072] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0073] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application. Content not described in detail in this specification belongs to the prior art known to those skilled in the art.

Claims

1. A method for protecting an asynchronous motor from stall heating, characterized in that: During the stall heating process, the winding phase sequence of the current injection is switched periodically, and the injected d-axis current is controlled in stages during each commutation.

2. The method for stall heating protection of an asynchronous motor according to claim 1, characterized in that, The step of periodically switching the winding phase sequence of current injection according to a preset commutation time interval and commutation sequence includes: During the first phase of the stalled rotor heating process, current is injected into the first phase winding and the second phase winding; After the commutation interval, the second period begins, during which current is injected and switched to the second and third phase windings. After the commutation interval, the third period begins, during which current is injected and switched between the third phase winding and the first phase winding. The phase commutation operation is repeated in the first time period, the second time period, and the third time period until the heating stop condition is met.

3. The method for stall heating protection of an asynchronous motor according to claim 1, characterized in that, The step of controlling the d-axis current injected in each cycle during each commutation in a staged manner includes: Gradual rise phase: After receiving the stall heating command, the d-axis current is controlled to rise from the initial value to the target value according to the preset first current change slope; Maintenance phase: After the d-axis current reaches the target value, the target value is maintained for a preset maintenance time; Rapid descent phase: When the heating stop condition is met, the d-axis current is reduced from the target value to the initial value according to the preset second current change slope; The slope of the first current change is less than the slope of the second current change.

4. The method for stall heating protection of an asynchronous motor according to claim 3, characterized in that, During the gradual increase phase, the d-axis current increases linearly according to the following formula: Id = Id0 + ΔIup × t1; Where Id is the real-time d-axis current, Id0 is the initial value, ΔIup is the slope of the first current change, and t1 is the rise time of the d-axis current from the initial value to the target value.

5. The method for stall heating protection of an asynchronous motor according to claim 3, characterized in that, During the rapid descent phase, the d-axis current decreases linearly according to the following formula: Id = Id1 - ΔIdown × t3; Where Id is the real-time d-axis current, Id1 is the target value, ΔIdown is the slope of the second current change, and t3 is the time it takes for the d-axis current to decrease from the target value to the initial value.

6. The method for stall heating protection of an asynchronous motor according to claim 3, characterized in that: One or more of the commutation time interval, the first current change slope, the second current change slope, the holding time, and the target value can be adjusted according to the characteristics of the motor and the battery.

7. A motor controller, characterized in that: The motor controller is configured to perform the stall heating protection method for an asynchronous motor as described in any one of claims 1 to 6.

8. A motor control system, characterized in that: Includes the motor controller as described in claim 7.

9. A computer-readable storage medium storing a computer program thereon, characterized in that: When the computer program is executed by the processor, it implements the steps of the stall heating protection method for the asynchronous motor as described in any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that: When the computer program is run, the stall heating protection method for the asynchronous motor as described in any one of claims 1-6 is executed.

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