Demagnetization protection method and device of motor, medium, controller and program product

Abstract

The invention provides a motor demagnetization protection method and device, a medium, a controller and a program product. The method comprises the following steps: acquiring a torque current ratio of a motor at a set motor temperature, a permanent magnet flux linkage value of the motor at the set motor temperature and a permanent magnet flux linkage value of the motor at the current motor temperature; calculating a torque difference corresponding to a temperature difference value between the current motor temperature and the set motor temperature according to the permanent magnet flux linkage value of the motor at the current motor temperature and the permanent magnet flux linkage value of the motor at the set motor temperature; according to the obtained torque current ratio and the torque difference obtained through calculation, whether irreversible demagnetization happens to the motor or not is judged; and if the irreversible demagnetization of the motor is judged, reducing the maximum current value limit value output by the controller so as to carry out demagnetization protection on the motor. According to the scheme of the invention, the motor can be prevented from further irreversible demagnetization under the condition that the permanent magnet continuously works in a strong countermagnetic field after irreversible demagnetization occurs.

Description

Technical Field

[0001] The present invention relates to the field of control, and in particular to a demagnetization protection method, device, medium, controller and program product for a motor. Background Art

[0002] As people pay more and more attention to environmental protection and efficient use of energy, the wave of automobile electrification is becoming more and more surging. For new energy vehicles, battery technology, motor technology, and motor controller technology are called the three key electric technologies of new energy vehicles. Under the premise that current battery technology has not made a breakthrough, improving the efficiency, power density, safety and reliability of the motor drive system has become the main research direction of the motor drive system of new energy vehicles.

[0003] Permanent magnet assisted synchronous reluctance motors are widely used in pure electric or hybrid new energy vehicles because of their high power density, wide speed range, small size, high efficiency, etc. Compared with other types of motors, permanent magnet motors have some unsurpassed advantages, but also some disadvantages. Since the magnetic steel material commonly used in permanent magnet assisted synchronous reluctance motors is ferrite, the magnetic steel of this material has low residual magnetic density and coercive force, and is prone to irreversible demagnetization, affecting the normal operation of the motor.

[0004] When the permanent magnet assisted synchronous reluctance motor works in strong reverse magnetic field, high temperature and other harsh working conditions, the permanent magnets in the motor may be irreversibly demagnetized, resulting in a decrease in motor performance. After the motor is irreversibly demagnetized, if the permanent magnets in the motor continue to work in the strong reverse magnetic field, the permanent magnets will be further irreversibly demagnetized, resulting in a significant decrease in the motor torque, affecting the output performance of the motor, and even damaging the entire drive system in severe cases, affecting the safety and reliability of the motor drive system. Summary of the invention

[0005] The main purpose of the present invention is to overcome the defects of the above-mentioned related technologies and provide a demagnetization protection method, device, medium, controller and program product for a motor to solve the problem in the related technology that after the permanent magnet assisted synchronous reluctance motor undergoes irreversible demagnetization, the permanent magnets in the motor continue to work under strong reverse magnetic field conditions, which will cause further irreversible demagnetization of the permanent magnets.

[0006] On the one hand, the present invention provides a demagnetization protection method for a motor, comprising: obtaining the torque-to-current ratio of the motor at a set motor temperature, the permanent magnet flux linkage value of the motor at the set motor temperature, and the permanent magnet flux linkage value of the motor at a current motor temperature; calculating a torque difference corresponding to a temperature difference between a current motor temperature and the set motor temperature according to the permanent magnet flux linkage value of the motor at the current motor temperature and the permanent magnet flux linkage value of the motor at the set motor temperature; judging whether irreversible demagnetization occurs to the motor according to the obtained torque-to-current ratio of the motor and the calculated torque difference; if it is judged that irreversible demagnetization occurs to the motor, reducing a maximum current value limit value output by a controller of the motor to perform demagnetization protection on the motor.

[0007] Optionally, obtaining a permanent magnet flux value of the motor at a current motor temperature includes:

[0008] The permanent magnet flux linkage value of the motor at the current motor temperature is calculated according to the current motor temperature and the permanent magnet flux linkage value of the motor at the set motor temperature.

[0009] Optionally, according to the permanent magnet flux value of the motor at the current motor temperature and the permanent magnet flux value of the motor at the set motor temperature, calculating the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature, including: according to the permanent magnet flux value of the motor at the current motor temperature, the permanent magnet flux value of the motor at the set motor temperature and the current quadrature-axis current of the motor, calculating the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature according to the following calculation formula:

[0010]

[0011] Wherein, ΔT is the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature, P is the number of motor pole pairs, ψ t is the permanent magnet flux value of the motor when the motor temperature is t, is the permanent magnet flux value of the motor when the motor temperature is the set motor temperature t0, i q is the current q-axis current of the motor.

[0012] Optionally, judging whether irreversible demagnetization has occurred in the motor is based on the acquired torque-current ratio of the motor and the calculated torque difference, including: judging whether the motor's unit current output torque has decreased, and whether the reduction ratio is greater than or equal to a preset ratio value, based on the torque-current ratio and the torque difference; if it is judged that the motor's unit current output torque has decreased and the reduction ratio is greater than or equal to a preset ratio value, then it is determined that irreversible demagnetization has occurred in the motor.

[0013] Optionally, if it is determined that irreversible demagnetization occurs in the motor, reducing the maximum current value limit value output by the controller of the motor comprises: reducing the maximum current value limit value output by the controller of the motor according to the reduction amount of the unit current output torque of the motor, wherein the reduction value ΔImax of the maximum current value limit value output by the controller of the motor is obtained according to the following formula:

[0014]

[0015] Among them, Imax is the maximum current value limit value output by the controller of the motor before reduction, T0 is the output torque of the motor under the current working condition, and I0 is the motor current under the current working condition.

[0016] On the other hand, the present invention provides a demagnetization protection device for a motor, comprising: an acquisition unit, used to acquire the torque-current ratio of the motor at a set motor temperature, the permanent magnet flux value of the motor at the set motor temperature, and the permanent magnet flux value of the motor at the current motor temperature; a calculation unit, used to calculate the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature according to the permanent magnet flux value of the motor at the current motor temperature and the permanent magnet flux value of the motor at the set motor temperature; a judgment unit, used to judge whether irreversible demagnetization has occurred in the motor according to the acquired torque-current ratio of the motor and the calculated torque difference; a protection unit, used to reduce the maximum current value limit value output by the controller of the motor if the demagnetization judgment unit judges that irreversible demagnetization has occurred to protect the motor from demagnetization.

[0017] Optionally, the acquisition unit acquires the permanent magnet flux value of the motor at the current motor temperature, including: calculating the permanent magnet flux value of the motor at the current motor temperature based on the current motor temperature and the permanent magnet flux value of the motor at the set motor temperature.

[0018] Optionally, the calculation unit calculates the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature according to the permanent magnet flux value of the motor at the current motor temperature and the permanent magnet flux value of the motor at the set motor temperature, including: calculating the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature according to the following calculation formula according to the permanent magnet flux value of the motor at the current motor temperature, the permanent magnet flux value of the motor at the set motor temperature and the current quadrature-axis current of the motor:

[0019]

[0020] Wherein, ΔT is the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature, P is the number of motor pole pairs, ψ t is the permanent magnet flux value of the motor when the motor temperature is t, is the permanent magnet flux value of the motor when the motor temperature is the set motor temperature t0, i q is the current q-axis current of the motor.

[0021] Optionally, the judgment unit judges whether the motor has irreversible demagnetization based on the acquired torque-current ratio of the motor and the calculated torque difference, including: judging whether the unit current output torque of the motor has decreased, and whether the reduction ratio is greater than or equal to a preset ratio value, based on the torque-current ratio and the torque difference; if it is judged that the unit current output torque of the motor has decreased and the reduction ratio is greater than or equal to a preset ratio value, it is determined that the motor has irreversible demagnetization.

[0022] Optionally, if the demagnetization judgment unit judges that irreversible demagnetization occurs in the motor, the protection unit reduces the maximum current value limit value output by the controller of the motor, including: reducing the maximum current value limit value output by the controller of the motor according to the reduction amount of the unit current output torque of the motor, wherein the reduction value ΔImax of the maximum current value limit value output by the controller of the motor is obtained according to the following formula:

[0023]

[0024] Among them, Imax is the maximum current value limit value output by the controller of the motor before reduction, T0 is the output torque of the motor under the current working condition, and I0 is the motor current under the current working condition.

[0025] Another aspect of the present invention provides a storage medium having a computer program stored thereon, wherein the program implements the steps of any of the aforementioned methods when executed by a processor.

[0026] Another aspect of the present invention provides a motor controller, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of any of the aforementioned methods when executing the program.

[0027] In another aspect, the present invention provides a motor controller, comprising any one of the above-mentioned demagnetization protection devices for the motor.

[0028] In yet another aspect, the present invention provides a computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the steps of any of the aforementioned methods are implemented.

[0029] According to the technical solution of the present invention, when irreversible demagnetization occurs in the motor, the maximum current limit value output by the controller is reduced to prevent the permanent magnet in the motor from continuing to work under a strong reverse magnetic field condition and further irreversible demagnetization, thereby ensuring the safety and reliability of the motor.

[0030] According to the technical solution of the present invention, the torque difference generated by the motor temperature difference is calculated, and the motor is judged whether irreversible demagnetization occurs according to the actual torque difference output by the motor and the calculated torque difference, thereby eliminating the influence of reversible demagnetization of the motor on the protection strategy judgment. If it is judged that the motor has irreversible demagnetization, the maximum current limit value of the controller output is reduced accordingly according to the degree of demagnetization, so as to prevent the motor from further more serious irreversible demagnetization and avoid more serious failures of the entire drive system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0032] Figure 1 1 is a schematic diagram of a method of an embodiment of a demagnetization protection method for a motor provided by the present invention;

[0033] Figure 2 A schematic diagram showing the change of ferrite remanence with temperature is shown;

[0034] Figure 3 is a method schematic diagram of a specific embodiment of the demagnetization protection method for a motor provided by the present invention;

[0035] Figure 4 It is a structural block diagram of an embodiment of a demagnetization protection device for a motor provided by the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0038] The permanent magnet of ferrite material has a large specific temperature coefficient, the remanence of the permanent magnet is greatly affected by temperature, and reversible demagnetization also occurs when the motor is running. Figure 2 The figure shows the change of ferrite remanence with temperature. The horizontal axis represents temperature, unit: °C, and the vertical axis represents the remanence Br of the permanent magnet, unit: tesla.

[0039] Reversible demagnetization generally refers to the decrease of the permanent magnet flux in the motor due to the increase of temperature, but when the temperature returns to room temperature, the permanent magnet flux returns to its original size. Irreversible demagnetization refers to the permanent magnet being in a strong reverse magnetic field, which causes the permanent magnet flux to decrease irreversibly.

[0040] The present invention provides a demagnetization protection method for a motor, which is particularly suitable for a permanent magnet assisted synchronous reluctance motor.

[0041] Figure 1 It is a method schematic diagram of an embodiment of the demagnetization protection method of a motor provided by the present invention.

[0042] like Figure 1 As shown, according to one embodiment of the present invention, the demagnetization protection method of the motor includes at least step S110, step S120, step S130 and step S140.

[0043] Step S110, obtaining the torque-to-current ratio of the motor at a set motor temperature, the permanent magnet flux linkage value of the motor at the set motor temperature, and the permanent magnet flux linkage value of the motor at the current motor temperature.

[0044] The torque-to-current ratio of the motor is the ratio of the output torque of the motor to the output current of the controller of the motor. Specifically, the motor is first calibrated, and the output current of the controller of the motor under different working conditions is collected. The different working conditions include different motor speeds and torques. The torque-to-current ratio T / I of the motor at the set motor temperature and the permanent magnet flux value ψ of the motor at the set motor temperature t0 are collected.t0 , T represents the output torque of the motor, and I represents the current of the motor. The set motor temperature is, for example, 25°C.

[0045] In a specific implementation, obtaining the permanent magnet flux linkage value of the motor at the current motor temperature includes: calculating the permanent magnet flux linkage value of the motor at the current motor temperature based on the current motor temperature and the permanent magnet flux linkage value of the motor at the set motor temperature.

[0046] Specifically, the motor temperature under any working condition is collected, and the permanent magnet flux value of the motor under the set motor temperature t0 is calculated based on the currently collected motor temperature Calculate the permanent magnet flux value of the motor at the current motor temperature. In a specific implementation, based on the current motor temperature and the permanent magnet flux value of the motor at the set motor temperature, the permanent magnet flux value of the motor at the current motor temperature is calculated according to the following formula:

[0047]

[0048] Among them, ψ t is the permanent magnet flux value of the motor when the motor temperature is t, is the permanent magnet flux linkage value of the motor when the motor temperature is the set motor temperature t0, and α is the specific temperature coefficient of the permanent magnet, for example, -0.18% / °C.

[0049] Step S120 , calculating a torque difference corresponding to a temperature difference between the current motor temperature and the set motor temperature according to the permanent magnet flux value of the motor at the current motor temperature and the permanent magnet flux value of the motor at the set motor temperature.

[0050] The torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature, that is, the torque difference generated by the temperature difference between the current motor temperature and the set motor temperature. In a specific implementation, according to the permanent magnet flux value of the motor at the current motor temperature, the permanent magnet flux value of the motor at the set motor temperature, and the current quadrature axis current of the motor, the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature is calculated according to the following calculation formula:

[0051]

[0052] Wherein, ΔT is the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature, P is the number of motor pole pairs, ψ t is the permanent magnet flux value of the motor when the motor temperature is t, is the permanent magnet flux value of the motor when the motor temperature is the set motor temperature t0, i q is the current q-axis current of the motor.

[0053] Step S130, judging whether irreversible demagnetization occurs in the motor according to the acquired torque-to-current ratio of the motor and the calculated torque difference.

[0054] In a specific embodiment, based on the torque-to-current ratio and the torque difference, it is determined whether the motor's unit current output torque is reduced, and whether the reduction ratio is greater than or equal to a preset ratio value; if it is determined that the motor's unit current output torque is reduced and the reduction ratio is greater than or equal to the preset ratio value, it is determined that irreversible demagnetization has occurred in the motor; if it is determined that the motor's unit current output torque is not reduced or the reduction value is less than the preset ratio value, it is determined that the motor is operating normally and no processing is performed.

[0055] Specifically, the motor unit current output torque is equal to (T0+ΔT) / I0; the motor unit current output torque reduction value is equal to T / I-(T0+ΔT) / I0, then the motor unit current output torque reduction ratio is Wherein, T0 is the output torque of the motor under the current working condition, and I0 is the motor current under the current working condition. Assume that the preset ratio value is a, that is, to determine whether (T0+ΔT) / I0<T / I is satisfied, and If not satisfied, that is, (T0+ΔT) / I0≥T / I, or The motor is determined to be operating normally and the controller does not process it. If (T0+ΔT) / I0<T / I, and That is, if the unit current output torque decreases and the reduction ratio exceeds the preset ratio value a, it is determined that irreversible demagnetization has occurred in the motor.

[0056] According to the above embodiment, whether the motor has irreversible demagnetization is determined by whether the motor flux is reduced. The motor flux value is reduced by a preset ratio value (the preset ratio value range includes, for example, 1.5% to 3%, for example, 1.5%, i.e., 0.015) or more before the motor is determined to have irreversible demagnetization. The motor unit current output torque T / I is proportional to the motor flux, so whether the motor has irreversible demagnetization is determined based on the degree of reduction of the motor unit current output torque T / I.

[0057] Step S140: If it is determined that irreversible demagnetization occurs in the motor, the maximum current limit value output by the controller of the motor is reduced to protect the motor from demagnetization.

[0058] Specifically, if it is determined that the motor has irreversible demagnetization, the maximum current value limit value output by the motor controller is reduced according to the reduction in the unit current output torque of the motor to prevent the motor from further irreversible demagnetization.

[0059] In a specific implementation manner, the reduction value ΔImax of the maximum current limit value output by the controller of the motor is obtained according to the following formula:

[0060]

[0061] That is, the maximum current limit value of the motor output controller is set to I max -ΔI max ; Wherein, Imax is the maximum current limit value output by the controller of the motor before reduction, and ΔImax is the reduction value of the maximum current limit value output by the controller of the motor:

[0062]

[0063] Wherein, T0 is the motor torque of the motor under the current working condition, and I0 is the motor current under the current working condition, that is, T0 and I0 are the motor torque and motor current of the motor under any working condition, respectively. That is, T0 is the motor torque of the motor under any working condition, and I0 is the motor current under the same working condition (the same working condition as T0).

[0064] For example, if the unit current output torque decreases by more than 1.5%, it is determined that the motor has irreversibly demagnetized, and the motor controller MCU is driven to reduce the controller output according to the unit current output torque reduction, and the controller output maximum current value limit value The maximum current limit of the controller output is set to I max -ΔI max To prevent the motor from further irreversible demagnetization. Preferably, after reducing the maximum current limit value output by the motor controller, the motor torque current ratio T / I is updated to determine again whether the motor has irreversible demagnetization and perform demagnetization protection.

[0065] According to the above embodiment of the present invention, the difference in the flux linkage of the permanent magnet of the motor at two different temperatures is calculated based on the motor temperature difference, thereby calculating the torque difference caused by the motor temperature difference (i.e., the motor undergoes reversible demagnetization), and the actual motor output torque difference is compared with the calculated torque difference. If the actual motor output torque difference is greater than the calculated torque difference, it is determined that the motor undergoes irreversible demagnetization. The influence of the reversible demagnetization of the motor on the judgment of the protection strategy is eliminated. If it is determined that the motor undergoes irreversible demagnetization, the controller output maximum current value limit value is correspondingly reduced according to the degree of demagnetization to prevent the motor from further undergoing more serious irreversible demagnetization.

[0066] In order to clearly illustrate the technical solution of the present invention, the execution process of the demagnetization protection method for the motor provided by the present invention is described below with reference to a specific embodiment.

[0067] Figure 3 FIG. 1 is a schematic diagram of a method for demagnetization protection of a motor provided by the present invention in a specific embodiment. Figure 3 As shown:

[0068] Step 1: Calibrate the motor and collect the torque-to-current ratio T / I of the motor at a certain temperature;

[0069] Step 2: Collect the motor temperature under any working condition of the motor and calculate the permanent magnet flux of the motor at that temperature. For example, if t0 is 25°C, then ψ t =ψ 25℃ ×[1+α(t-25℃)];

[0070] Step 3: Calculate the torque difference caused by the motor temperature difference: ΔT = P(ψ 25℃ -ψ t )i q ;

[0071] Step 4: Determine whether the motor output torque per unit current is reduced, that is, whether:

[0072] (T0+ΔT) / I0<T / I, and

[0073] Step 5: If the motor output torque per unit current does not decrease or decreases slightly, that is, (T0+ΔT) / I0≥T / I, or The motor is running normally and the controller does not take any action.

[0074] If the motor output torque per unit current decreases, that is, (T0+ΔT) / I0<T / I, and That is, if the unit current output torque decreases by more than 1.5%, it is determined that the motor has irreversibly demagnetized, and the motor controller MCU is driven to reduce the controller output maximum current limit value according to the unit current output torque reduction. The maximum current limit of the controller output is set to I max -ΔI max to prevent the motor from further irreversible demagnetization; at the same time, update the torque-to-current ratio T / I of the motor and return to step S2.

[0075] The present invention also provides a demagnetization protection device for a motor, which is particularly suitable for a permanent magnet assisted synchronous reluctance motor.

[0076] Figure 4FIG. 1 is a structural block diagram of an embodiment of a demagnetization protection device for a motor provided by the present invention. Figure 4 As shown, the demagnetization protection device 100 for a motor includes: an acquisition unit 110 , a calculation unit 120 , a judgment unit 130 and a protection unit 140 .

[0077] The acquisition unit 110 is used to acquire the torque-to-current ratio of the motor at a set motor temperature, the permanent magnet flux linkage value of the motor at the set motor temperature, and the permanent magnet flux linkage value of the motor at a current motor temperature.

[0078] The torque-to-current ratio of the motor is the ratio of the output torque of the motor to the output current of the controller of the motor. Specifically, the motor is first calibrated, and the output current of the controller of the motor under different working conditions is collected. The different working conditions include different motor speeds and torques. The torque-to-current ratio T / I of the motor at the set motor temperature and the permanent magnet flux value ψ of the motor at the set motor temperature t0 are collected. t0 , T represents the output torque of the motor, and I represents the current of the motor. The set motor temperature is, for example, 25°C.

[0079] In a specific implementation, the acquisition unit 110 acquires the permanent magnet flux value of the motor at the current motor temperature, including: calculating the permanent magnet flux value of the motor at the current motor temperature based on the current motor temperature and the permanent magnet flux value of the motor at the set motor temperature.

[0080] Specifically, the motor temperature under any working condition is collected, and the permanent magnet flux value of the motor under the set motor temperature t0 is calculated based on the currently collected motor temperature Calculate the permanent magnet flux value of the motor at the current motor temperature. In a specific implementation, based on the current motor temperature and the permanent magnet flux value of the motor at the set motor temperature, the permanent magnet flux value of the motor at the current motor temperature is calculated according to the following formula:

[0081]

[0082] Among them, ψ t is the permanent magnet flux value of the motor when the motor temperature is t, is the permanent magnet flux linkage value of the motor when the motor temperature is the set motor temperature t0, and α is the specific temperature coefficient of the permanent magnet, for example, -0.18% / °C.

[0083] The calculation unit 120 is used to calculate the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature according to the permanent magnet flux value of the motor at the current motor temperature and the permanent magnet flux value of the motor at the set motor temperature.

[0084] The torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature, that is, the torque difference generated by the temperature difference between the current motor temperature and the set motor temperature. In a specific implementation, according to the permanent magnet flux value of the motor at the current motor temperature, the permanent magnet flux value of the motor at the set motor temperature, and the current quadrature axis current of the motor, the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature is calculated according to the following calculation formula:

[0085]

[0086] Wherein, ΔT is the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature, P is the number of motor pole pairs, ψ t is the permanent magnet flux value of the motor when the motor temperature is t, is the permanent magnet flux value of the motor when the motor temperature is the set motor temperature t0, i q is the current q-axis current of the motor.

[0087] The judging unit 130 is configured to judge whether irreversible demagnetization occurs in the motor according to the acquired torque-to-current ratio of the motor and the calculated torque difference.

[0088] In a specific embodiment, based on the torque-to-current ratio and the torque difference, it is determined whether the motor's unit current output torque is reduced, and whether the reduction ratio is greater than or equal to a preset ratio value; if it is determined that the motor's unit current output torque is reduced and the reduction ratio is greater than or equal to the preset ratio value, it is determined that irreversible demagnetization has occurred in the motor; if it is determined that the motor's unit current output torque is not reduced or the reduction value is less than the preset ratio value, it is determined that the motor is operating normally and no processing is performed.

[0089] Specifically, the motor unit current output torque is equal to (T0+ΔT) / I0; the motor unit current output torque reduction value is equal to T / I-(T0+ΔT) / I0, then the motor unit current output torque reduction ratio is Wherein, T0 is the output torque of the motor under the current working condition, and I0 is the motor current under the current working condition. Assume that the preset ratio value is a, that is, to determine whether (T0+ΔT) / I0<T / I is satisfied, and If not satisfied, that is, (T0+ΔT) / I0≥T / I, or The motor is determined to be operating normally and the controller does not process it. If (T0+ΔT) / I0<T / I, and That is, if the unit current output torque decreases and the reduction ratio exceeds the preset ratio value a, it is determined that irreversible demagnetization has occurred in the motor.

[0090] According to the above embodiment, whether the motor has irreversible demagnetization is determined by whether the motor flux is reduced. The motor flux value is reduced by a preset ratio value (the preset ratio value range includes, for example, 1.5% to 3%, for example, 1.5%, i.e., 0.015) or more before the motor is determined to have irreversible demagnetization. The motor unit current output torque T / I is proportional to the motor flux, so whether the motor has irreversible demagnetization is determined based on the degree of reduction of the motor unit current output torque T / I.

[0091] The protection unit 140 is configured to reduce a maximum current limit value output by a controller of the motor if the demagnetization determination unit determines that irreversible demagnetization has occurred in the motor, so as to perform demagnetization protection on the motor.

[0092] Specifically, if it is determined that the motor has irreversible demagnetization, the maximum current value limit value output by the motor controller is reduced according to the reduction in the unit current output torque of the motor to prevent the motor from further irreversible demagnetization.

[0093] In a specific implementation manner, the reduction value ΔImax of the maximum current limit value output by the controller of the motor is obtained according to the following formula:

[0094]

[0095] That is, the maximum current limit value of the motor output controller is set to I max -ΔI max ; Wherein, Imax is the maximum current limit value output by the controller of the motor before reduction, and ΔImax is the reduction value of the maximum current limit value output by the controller of the motor:

[0096]

[0097] Wherein, T0 is the motor torque of the motor under the current working condition, and I0 is the motor current under the current working condition, that is, T0 and I0 are the motor torque and motor current of the motor under any working condition, respectively. That is, T0 is the motor torque of the motor under any working condition, and I0 is the motor current under the same working condition (the same working condition as T0).

[0098] For example, if the unit current output torque decreases by more than 1.5%, it is determined that the motor has irreversibly demagnetized, and the motor controller MCU is driven to reduce the controller output according to the unit current output torque reduction, and the controller output maximum current value limit value The maximum current limit of the controller output is set to I max -ΔI maxTo prevent the motor from further irreversible demagnetization. Preferably, after reducing the maximum current limit value output by the motor controller, the motor torque current ratio T / I is updated to determine again whether the motor has irreversible demagnetization and perform demagnetization protection.

[0099] The present invention also provides a storage medium corresponding to the demagnetization protection method of the motor, on which a computer program is stored, and when the computer program is executed by a processor, the steps of any of the above methods are implemented.

[0100] The present invention also provides a motor controller corresponding to the demagnetization protection method of the motor, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of any of the aforementioned methods when executing the computer program.

[0101] The present invention also provides a motor controller corresponding to the demagnetization protection device of the motor, comprising any of the demagnetization protection devices of the motor described above.

[0102] The present invention also provides a computer program product corresponding to the demagnetization protection method of the motor, comprising a computer program, and when the computer program is executed by a processor, the steps of any of the aforementioned methods are implemented.

[0103] Accordingly, the solution provided by the present invention reduces the maximum current limit value of the controller output when irreversible demagnetization occurs in the motor to prevent the permanent magnets in the motor from continuing to work under strong reverse magnetic field conditions and further irreversible demagnetization, thereby ensuring the safety and reliability of the motor.

[0104] According to the technical solution of the present invention, the torque difference generated by the motor temperature difference is calculated, and the motor is judged whether irreversible demagnetization occurs according to the actual torque difference output by the motor and the calculated torque difference, thereby eliminating the influence of reversible demagnetization of the motor on the protection strategy judgment. If it is judged that the motor has irreversible demagnetization, the maximum current limit value of the controller output is reduced accordingly according to the degree of demagnetization, so as to prevent the motor from further more serious irreversible demagnetization and avoid more serious failures of the entire drive system.

[0105] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored as one or more instructions or codes on a computer-readable medium or transmitted via a computer-readable medium. Other examples and implementations are within the scope and spirit of the present invention and the appended claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hard wiring, or a combination of any of these. In addition, each functional unit may be integrated into a processing unit, each unit may exist physically separately, or two or more units may be integrated into one unit.

[0106] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of the units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0107] The units described as separate components may or may not be physically separated, and the components of the control device may or may not be physical units, that is, they may be located in one place or distributed in multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0108] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the relevant technology or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, disk or optical disk and other media that can store program codes.

[0109] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A demagnetization protection method for a motor, characterized in that: include: Acquire the torque-to-current ratio of the motor at a set motor temperature, the permanent magnet flux linkage value of the motor at the set motor temperature, and the permanent magnet flux linkage value of the motor at a current motor temperature; Calculating a torque difference corresponding to a temperature difference between the current motor temperature and the set motor temperature according to a permanent magnet flux value of the motor at the current motor temperature and a permanent magnet flux value of the motor at the set motor temperature; Determining whether irreversible demagnetization occurs in the motor according to the acquired torque-to-current ratio of the motor and the calculated torque difference; If it is determined that irreversible demagnetization occurs to the motor, the maximum current limit value output by the controller of the motor is reduced to protect the motor from demagnetization.

2. The method according to claim 1, characterized in that Obtaining the permanent magnet flux value of the motor at the current motor temperature, including: The permanent magnet flux linkage value of the motor at the current motor temperature is calculated according to the current motor temperature and the permanent magnet flux linkage value of the motor at the set motor temperature.

3. The method according to claim 1, characterized in that Calculating a torque difference corresponding to a temperature difference between a current motor temperature and a set motor temperature according to a permanent magnet flux value of the motor at a current motor temperature and a permanent magnet flux value of the motor at a set motor temperature, including: According to the permanent magnet flux value of the motor at the current motor temperature, the permanent magnet flux value of the motor at the set motor temperature, and the current quadrature-axis current of the motor, the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature is calculated according to the following calculation formula: Wherein, ΔT is the torque difference corresponding to the temperature difference between the current motor temperature and the set motor temperature, P is the number of motor pole pairs, ψ t is the permanent magnet flux value of the motor when the motor temperature is t, is the permanent magnet flux value of the motor when the motor temperature is the set motor temperature t0, i q is the current q-axis current of the motor.

4. The method according to any one of claims 1 to 3, characterized in that: Judging whether irreversible demagnetization occurs in the motor according to the acquired torque-to-current ratio of the motor and the calculated torque difference, includes: According to the torque-to-current ratio and the torque difference, determining whether the motor output torque per unit current is reduced, and whether the reduction ratio is greater than or equal to a preset ratio value; If it is determined that the motor output torque per unit current decreases and the reduction ratio is greater than or equal to a preset ratio value, it is determined that irreversible demagnetization occurs in the motor.

5. The method according to claim 4, characterized in that If it is determined that irreversible demagnetization occurs in the motor, reducing the maximum current limit value output by the controller of the motor, including: According to the reduction in the unit current output torque of the motor, the maximum current limit value output by the motor controller is reduced, wherein the reduction value ΔImax of the maximum current limit value output by the motor controller is obtained according to the following formula: Among them, Imax is the maximum current value limit value output by the controller of the motor before reduction, and T0 and I0 are the motor torque and motor current of the motor under any working condition respectively.

6. A demagnetization protection device for a motor, characterized in that: include: An acquisition unit, used to acquire a torque-to-current ratio of the motor at a set motor temperature, a permanent magnet flux linkage value of the motor at the set motor temperature, and a permanent magnet flux linkage value of the motor at a current motor temperature; a calculation unit, configured to calculate a torque difference corresponding to a temperature difference between a current motor temperature and a set motor temperature according to a permanent magnet flux value of the motor at a current motor temperature and a permanent magnet flux value of the motor at the set motor temperature; a judging unit, configured to judge whether irreversible demagnetization occurs in the motor according to the acquired torque-to-current ratio of the motor and the calculated torque difference; The protection unit is used to reduce the maximum current limit value output by the controller of the motor if the demagnetization judgment unit judges that irreversible demagnetization occurs to the motor, so as to perform demagnetization protection on the motor.

7. The device according to claim 6, characterized in that The acquiring unit acquires the permanent magnet flux value of the motor at the current motor temperature, including: The permanent magnet flux linkage value of the motor at the current motor temperature is calculated according to the current motor temperature and the permanent magnet flux linkage value of the motor at the set motor temperature.

8. A storage medium, characterized in that: A computer program is stored thereon, and when the program is executed by a processor, the steps of any method described in claims 1-5 are implemented.

9. A motor controller, characterized in that: The invention comprises a processor, a memory and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the method described in any one of claims 1 to 5 are implemented, or the demagnetization protection device for the motor described in any one of claims 6 to 7 is included.

10. A computer program product, characterized in that The invention comprises a computer program, which implements the steps of any one of the methods of claims 1 to 5 when executed by a processor.

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