A motor control method, device, system, motor and electric appliance

Abstract

The application discloses a motor control method, device and system, a motor and an electrical equipment, and belongs to the field of motor control. When a motor enters a field weakening control state, a bus voltage of a frequency converter for controlling the motor is acquired. If a bus voltage drop value in a unit time is detected to exceed a preset voltage value, it is indicated that the bus voltage drops too fast. At this time, if the frequency is directly reduced, the frequency reduction speed is relatively slow, the operating current increases too fast, overcurrent protection is triggered, and the system is shut down. Therefore, the application scheme first increases the carrier frequency of the frequency converter to a preset carrier frequency, and then switches an integral term in a control parameter of the motor to a value corresponding to the preset carrier frequency. In this way, when the frequency is reduced, the frequency reduction speed of the motor can be accelerated, the operating current is prevented from increasing too fast, overcurrent protection is not triggered in the process in which the motor reduces the frequency and exits the field weakening control state, and normal operation of the system is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of motor control, in particular, to a motor control method, device, system, motor and electrical equipment. BACKGROUND

[0002] Motors are widely used in various fields, and their control mode is developing towards high precision and low cost. When the motor is running at high frequency, it will exit the constant torque zone and enter the constant power zone, and the frequency converter will also enter the field weakening control state. In order to meet the operating frequency requirements of the motor, when the electromotive force generated by the motor rotation is about to reach the bus voltage, the reverse excitation current needs to be increased to generate a reverse magnetic field to offset the part of the motor electromotive force exceeding the bus voltage. Due to the increase of the excitation current, the total load current of the motor increases rapidly. Therefore, in the reliability design of the frequency converter, a reasonable protection value needs to be set to avoid triggering system protection shutdown when the motor current increases rapidly, which affects the user experience.

[0003] However, in actual application process, the input voltage of the power grid is not always stable, and it may encounter high voltage, low voltage and other situations, and it may also encounter abnormal situations such as rapid voltage drop and rise. When the power grid voltage drops rapidly, the bus voltage of the frequency converter will follow the power grid voltage and decrease rapidly. At this time, since the motor is running at a constant frequency, the electromotive force of the motor does not change. At this time, the frequency converter control system must quickly adjust the excitation current according to the current voltage, so that the operating current increases suddenly. When the power grid voltage drops rapidly, the overcurrent protection is triggered, causing the system to shut down. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the present application provides a motor control method, device, system, motor and electrical equipment to solve the problem that when the motor is in the field weakening control state, if the power grid voltage drops rapidly, the overcurrent protection is triggered, causing the system to shut down.

[0005] The technical scheme adopted by the present application to solve its technical problems is:

[0006] In a first aspect, a motor control method is provided, comprising the following steps:

[0007] When the motor enters the field weakening control state, the bus voltage of the frequency converter for controlling the motor is obtained;

[0008] When the drop value of the bus voltage per unit time exceeds a preset voltage value, the carrier frequency of the frequency converter is controlled to increase to a preset carrier frequency, and the integral term in the control parameters of the motor is switched to a value corresponding to the preset carrier frequency;

[0009] The frequency of the motor is controlled to decrease until the motor exits the field weakening control state.

[0010] Further, further comprising:

[0011] Obtaining a field weakening angle of the motor;

[0012] If the field weakening angle is greater than a preset angle value, determining that the motor enters the field weakening control state.

[0013] Further, further comprising:

[0014] Obtaining a back electromotive force of the motor;

[0015] When the ratio of the back electromotive force to the bus voltage is greater than a preset ratio value, determining that the motor enters the field weakening control state.

[0016] Further, the exiting the field weakening control state comprises:

[0017] When the field weakening angle is not greater than the preset angle value, determining that the motor exits the field weakening control state.

[0018] Further, the exiting the field weakening control state comprises:

[0019] When the ratio of the back electromotive force to the bus voltage is less than the preset ratio value, determining that the motor exits the field weakening control state.

[0020] Further, the motor is a permanent magnet synchronous motor

[0021] In a second aspect, a motor control device is provided, comprising:

[0022] A bus voltage obtaining module, configured to obtain a bus voltage of a frequency converter for controlling the motor when the motor enters a field weakening control state;

[0023] A related parameter adjusting module, configured to control a carrier frequency of the frequency converter to increase to a preset carrier frequency and switch an integral term in a control parameter of the motor to a value corresponding to the preset carrier frequency when a drop value of the bus voltage per unit time exceeds a preset voltage value.

[0024] A motor frequency control module, configured to control the motor to reduce frequency until the motor exits the field weakening control state.

[0025] In a third aspect, a motor control system is provided, comprising:

[0026] A processor;

[0027] A memory for storing instructions executable by the processor;

[0028] The processor is configured to execute the method of any one of the first aspect.

[0029] In a fourth aspect, there is provided an electric machine controlled by the method of any one of the first aspect.

[0030] In a fifth aspect, there is provided an electric appliance comprising the electric machine of the fourth aspect.

[0031] Advantages:

[0032] The technical solution of the present application provides an electric machine control method, device, system, electric machine and electric appliance. When the electric machine enters a field weakening control state, the bus voltage of a frequency converter for controlling the electric machine is obtained. If it is detected that the bus voltage drop value in a unit time exceeds a preset voltage value, it indicates that the bus voltage drops too fast. At this time, if the frequency is directly reduced, the frequency reduction speed is slow, the operating current increases too fast, and the overcurrent protection is triggered, causing the system to shut down. Therefore, the present application increases the carrier frequency of the frequency converter to a preset carrier frequency, and then switches the integral term in the control parameter of the electric machine to a value corresponding to the preset carrier frequency. In this way, when the frequency is reduced, the frequency reduction speed of the electric machine can be accelerated, and the operating current can be prevented from increasing too fast. Therefore, during the process of reducing the frequency of the electric machine to exit the field weakening control state, the overcurrent protection is not triggered, and the system can operate normally. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without making any creative effort.

[0034] Figure 1 is a flow chart of an electric machine control method provided by an embodiment of the present application;

[0035] Figure 2 is a structural schematic diagram of an electric machine control device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present application more clear, the technical solutions of the present application will be described in detail below in combination with the drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making any creative effort are within the scope of protection of the present application.

[0037] In a first embodiment, referring to Figure 1 The embodiment of the present application provides an electric machine control method, comprising the following steps:

[0038] S11: acquiring bus voltage of a frequency converter for controlling the motor when the motor enters a field weakening control state;

[0039] S12: when a drop value of the bus voltage in a unit time exceeds a preset voltage value, increasing a carrier frequency of the frequency converter to a preset carrier frequency, and switching an integral term in a control parameter of the motor to a value corresponding to the preset carrier frequency;

[0040] S13: controlling the motor to decrease frequency until the motor exits the field weakening control state.

[0041] The motor control method provided by the embodiment of the application acquires bus voltage of a frequency converter for controlling the motor when the motor enters a field weakening control state; if it is detected that a drop value of the bus voltage in a unit time exceeds a preset voltage value, it indicates that the bus voltage drops too fast, and if frequency is directly decreased at this time, the frequency decrease speed is slow, the operating current increases too fast, and overcurrent protection is triggered, causing system shutdown. Therefore, the application scheme first increases the carrier frequency of the frequency converter to a preset carrier frequency, and then switches an integral term in a control parameter of the motor to a value corresponding to the preset carrier frequency, so that the frequency decrease speed of the motor can be accelerated when frequency is decreased, and the operating current is prevented from increasing too fast, and therefore overcurrent protection is not triggered during the process of decreasing frequency of the motor to exit the field weakening control state, and normal operation of the system is ensured.

[0042] The second embodiment, as a supplement to the first embodiment, the application provides a specific motor control method, and it needs to be noted that the existing motor directly performs frequency decrease when bus voltage drops when the motor enters a field weakening control state. However, the inventor finds in actual application that when the voltage drops too fast, the frequency decrease speed is too slow, and the current cannot be prevented from increasing fast, and therefore the current increases rapidly, and overcurrent protection is triggered.

[0043] To solve this technical problem, the embodiment of the application acquires bus voltage of a frequency converter for controlling the motor when the motor enters a field weakening control state; in one embodiment, the motor entering the field weakening control state is judged by using a field weakening angle; specifically, the field weakening angle of the motor is acquired; if the field weakening angle is greater than a preset angle value, it is judged that the motor enters the field weakening control state. In another embodiment, the motor entering the field weakening control state is judged by using back electromotive force; specifically, the back electromotive force of the motor is acquired; when a ratio of the back electromotive force to the bus voltage is greater than a preset ratio value, it is judged that the motor enters the field weakening control state.

[0044] When the drop value of the bus voltage in a unit time exceeds a preset voltage value, the carrier frequency a of the frequency converter is raised to a preset carrier frequency b, and the integral term in the control parameter of the motor is switched to a value corresponding to the preset carrier frequency b; wherein the drop value of the bus voltage = (bus voltage at the current time - bus voltage at the last time) / (current time - last time); the integral term in the control parameter of the motor includes the integral term coefficient of the PI link in the speed loop, the current loop and the phase-locked loop, and the corresponding relationship between the preset carrier frequency and the integral term coefficient of the PI link in the speed loop, the current loop and the phase-locked loop is stored in advance, and when the carrier frequency is changed, the integral term can be changed directly through the stored corresponding relationship. By raising the carrier frequency and replacing the integral term value, the system response speed can be improved, which can provide a basic condition for rapid frequency reduction of the motor, and at the same time will not affect the frequency converter loss when the motor is normally operated.

[0045] Finally, the motor is controlled to reduce the frequency until the weak magnetic control state is exited. Since the system quickly exits the weak magnetic state, and the load current is also reduced during the frequency reduction process, the design requirements of high reliability and uninterrupted operation of the product are ensured.

[0046] As an optional implementation manner of the embodiment of the application, judging the exit of the weak magnetic control state comprises: when the weak magnetic angle is not greater than a preset angle value, judging that the motor exits the weak magnetic control state.

[0047] As another optional implementation manner of the embodiment of the application, judging the exit of the weak magnetic control state comprises: when the ratio of the back electromotive force to the bus voltage is less than a preset ratio value, judging that the motor exits the weak magnetic control state.

[0048] It can be understood that after the weak magnetic control state is exited, the carrier frequency of the frequency converter is restored to the original carrier frequency a, and the integral term in the control parameter of the motor is restored to the value corresponding to the original carrier frequency a, so as to ensure that the original control can be restored after the weak magnetic control state is exited.

[0049] Because the permanent magnet synchronous motor has the characteristics of low frequency high torque, constant torque output and wide operation range, as a preferred implementation manner of the embodiment of the application, the motor in the embodiment of the application is a permanent magnet synchronous motor.

[0050] The specific motor control method provided by the embodiment of the application can solve the problem of system failure caused by the sudden increase of operating current when the motor enters the high-frequency operation, the motor control state enters the field weakening control, and the bus voltage drops due to the drop of grid input voltage. The reason for the sudden increase of operating current is that the motor control field weakening angle increases due to the decrease of bus voltage. At this time, the motor is only required to be quickly reduced in frequency and exit the field weakening control region, so as to solve the problem of system failure caused by the sudden increase of operating current. The carrier frequency of the frequency converter is increased to the preset carrier frequency, and the integral term in the control parameter of the motor is switched to the value corresponding to the preset carrier frequency. In this way, the motor frequency reduction speed can be accelerated when the frequency reduction is performed, and the operating current is prevented from increasing too fast, so that the overcurrent protection is not triggered during the process of motor frequency reduction and exit from the field weakening control state, and the normal operation of the system is ensured.

[0051] In a third embodiment, the application provides a motor control device, as shown in the accompanying drawings, comprising: Figure 2

[0052] The bus voltage acquisition module 21 is configured to acquire the bus voltage of the frequency converter for controlling the motor when the motor enters the field weakening control state. The determination of whether the motor enters the field weakening control device includes: acquiring the field weakening angle of the motor; and determining that the motor enters the field weakening control state when the field weakening angle is greater than a preset angle value. Alternatively, the back electromotive force of the motor is acquired; and the motor is determined to enter the field weakening control state when the ratio of the back electromotive force to the bus voltage is greater than a preset ratio.

[0053] The related parameter adjustment module 22 is configured to increase the carrier frequency of the frequency converter to a preset carrier frequency and switch the integral term in the control parameter of the motor to a value corresponding to the preset carrier frequency when the drop of the bus voltage in a unit time exceeds a preset voltage value.

[0054] The motor frequency control module 23 is configured to control the motor to reduce in frequency until the motor exits the field weakening control state. The exit of the motor from the field weakening control state includes: determining that the motor exits the field weakening control state when the field weakening angle is not greater than a preset angle value. Alternatively, the motor is determined to exit the field weakening control state when the ratio of the back electromotive force to the bus voltage is less than a preset ratio.

[0055] As a preferred implementation manner of the embodiment of the application, the motor in the embodiment of the application is a permanent magnet synchronous motor.

[0056] ​The motor control device provided by the embodiment of the application, when the motor enters a field weakening control state, a bus voltage acquisition module acquires a bus voltage of a frequency converter for controlling the motor; when a drop value of the bus voltage in a unit time exceeds a preset voltage value, a related parameter adjustment module controls a carrier frequency of the frequency converter to increase to a preset carrier frequency, and switches an integral term in a control parameter of the motor to a value corresponding to the preset carrier frequency; and a motor frequency control module controls the motor to decrease in frequency until the motor exits the field weakening control state. The motor control device provided by the embodiment of the application first increases the carrier frequency of the frequency converter to the preset carrier frequency, and then switches the integral term in the control parameter of the motor to the value corresponding to the preset carrier frequency, so that the motor can be decreased in frequency at a faster speed when the frequency is decreased, and the running current can be prevented from increasing too fast, so that the overcurrent protection is not triggered during the process of decreasing the frequency of the motor to exit the field weakening control state, and the system can be ensured to operate normally.

[0057] In a fourth embodiment, the application provides a motor control system, comprising:

[0058] a processor;

[0059] a memory for storing processor-executable instructions;

[0060] The processor is configured to execute the motor control method provided by the first embodiment or the second embodiment.

[0061] The motor control system provided by the embodiment of the application stores the executable instructions of the processor in the memory, and when the executable instructions are executed, the processor can acquire the bus voltage of the frequency converter for controlling the motor when the motor enters the field weakening control state; if it is detected that the drop value of the bus voltage in a unit time exceeds a preset voltage value, it indicates that the bus voltage drops too fast, and if the frequency is directly decreased at this time, the frequency decrease speed is slow, the running current increases too fast, the overcurrent protection is triggered, and the system is shut down. Therefore, the application first increases the carrier frequency of the frequency converter to the preset carrier frequency, and then switches the integral term in the control parameter of the motor to the value corresponding to the preset carrier frequency, so that the motor can be decreased in frequency at a faster speed when the frequency is decreased, the running current can be prevented from increasing too fast, the overcurrent protection is not triggered during the process of decreasing the frequency of the motor to exit the field weakening control state, and the system can be ensured to operate normally.

[0062] In a fifth embodiment, the application provides a motor controlled by the motor control method provided by the first embodiment or the second embodiment.

[0063] The motor provided by the embodiment of the application is controlled by the control method of the first embodiment or the second embodiment, so that when the motor enters the field weakening control state, the bus voltage of the frequency converter for controlling the motor is obtained; if it is detected that the bus voltage drop value in a unit time exceeds a preset voltage value, it indicates that the bus voltage drops too fast, at this time, if the frequency is directly reduced, the frequency reduction speed is slow, the operating current increases too fast, and the overcurrent protection is triggered, causing the system to shut down. Therefore, the application scheme first increases the carrier frequency of the frequency converter to a preset carrier frequency, and then switches the integral term in the control parameter of the motor to a value corresponding to the preset carrier frequency, so that when the frequency reduction is performed, the frequency reduction speed of the motor can be accelerated, and the operating current can be prevented from increasing too fast, so that during the process of reducing the frequency of the motor to exit the field weakening control state, the overcurrent protection is not triggered, and the normal operation of the motor is ensured.

[0064] In a sixth embodiment, the application provides an electrical appliance, which comprises the motor provided by the fifth embodiment.

[0065] The electrical appliance provided by the embodiment of the application is controlled by the control method of the first embodiment or the second embodiment, so that when the motor enters the field weakening control state, the bus voltage of the frequency converter for controlling the motor is obtained; if it is detected that the bus voltage drop value in a unit time exceeds a preset voltage value, it indicates that the bus voltage drops too fast, at this time, if the frequency is directly reduced, the frequency reduction speed is slow, the operating current increases too fast, and the overcurrent protection is triggered, causing the system to shut down. Therefore, the application scheme first increases the carrier frequency of the frequency converter to a preset carrier frequency, and then switches the integral term in the control parameter of the motor to a value corresponding to the preset carrier frequency, so that when the frequency reduction is performed, the frequency reduction speed of the motor can be accelerated, and the operating current can be prevented from increasing too fast, so that during the process of reducing the frequency of the motor to exit the field weakening control state, the overcurrent protection is not triggered, and the normal operation of the system is ensured.

[0066] It can be understood that the same or similar parts in the above embodiments can be mutually referred to, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0067] It should be noted that, in the description of the present application, the terms "first", "second", etc. are only for the purpose of description, and cannot be understood as indicating or implying relative importance. In addition, in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is at least two.

[0068] Any processes or methods described in the flowcharts or elsewhere in this specification can be understood as representing one or more modules, segments, or portions of code that includes executable instructions for performing specific logical functions or steps, and the various embodiments of the application can include additional or fewer steps performing the same or equivalent functions in the same or equivalent order as those described and shown in the figures. The various embodiments of the application can be implemented in software, hardware, firmware, or a combination thereof.

[0069] It should be understood that portions of the application can be implemented in hardware, software, firmware, or combinations thereof. In the above embodiments, the various steps or methods can be implemented in software or firmware that is stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, and in another embodiment, any of the following technologies, known in the art, or their combinations can be used: discrete logic circuitry having logic gates for implementing logic functions on data signals, application specific integrated circuits having appropriate combinational logic gates, programmable gate arrays (PGA), field programmable gate arrays (FPGA), and the like.

[0070] Those skilled in the art can understand that all or part of the steps carried out by the above-mentioned embodiments can be completed by programs instructing related hardware, and the programs can be stored in a computer readable storage medium, and when executed, include one or a combination of steps of the method embodiments.

[0071] In addition, the functional units in each embodiment of the present application can be integrated into one processing module, or each unit can be physically present alone, or two or more units can be integrated into one module. The above-mentioned integrated module can be realized in the form of hardware or in the form of a software function module. When the integrated module is realized in the form of a software function module and sold or used as an independent product, it can also be stored in a computer readable storage medium.

[0072] The above-mentioned storage medium can be a read-only memory, a magnetic disk or an optical disk, etc.

[0073] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0074] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and that those skilled in the art can make changes, modifications, substitutions and variations to the above-described embodiments within the scope of the present application.

Claims

1. A motor control method, characterized in that, Includes the following steps: When the motor enters the field weakening control state, the bus voltage of the frequency converter controlling the motor is obtained; When the decrease in the bus voltage per unit time exceeds the preset voltage value, the carrier frequency of the inverter is increased to the preset carrier frequency, and the integral term in the motor control parameters is switched to the value corresponding to the preset carrier frequency; the integral term is the integral coefficient of the PI element in the speed loop, current loop and phase-locked loop. Control the motor to reduce its frequency until it exits the field weakening control state.

2. The method according to claim 1, characterized in that, Also includes: Obtain the field weakening angle of the motor; If the field weakening angle is greater than the preset angle value, it is determined that the motor enters the field weakening control state.

3. The method according to claim 1, characterized in that, Also includes: Obtain the back electromotive force of the motor; When the ratio of the back electromotive force to the bus voltage is greater than a preset ratio, it is determined that the motor enters the field weakening control state.

4. The method according to claim 2, characterized in that: Exiting the field weakening control state includes: When the field weakening angle is not greater than the preset angle value, it is determined that the motor exits the field weakening control state.

5. The method according to claim 3, characterized in that: Exiting the field weakening control state includes: When the ratio of the back electromotive force to the bus voltage is less than the preset ratio, it is determined that the motor exits the field weakening control state.

6. The method according to claim 1, characterized in that: The motor is a permanent magnet synchronous motor.

7. A motor control device, characterized in that, include: The bus voltage acquisition module is used to acquire the bus voltage of the frequency converter controlling the motor when the motor enters the field weakening control state. The relevant parameter adjustment module is used to control the carrier frequency of the frequency converter to increase to the preset carrier frequency when the decrease value of the bus voltage per unit time exceeds the preset voltage value, and to switch the integral term in the control parameters of the motor to the value corresponding to the preset carrier frequency; the integral term is the integral coefficient of the PI link in the speed loop, current loop and phase-locked loop; The motor frequency control module is used to control the motor to reduce its frequency until it exits the field weakening control state.

8. A motor control system, characterized in that, include: processor; Memory used to store the processor's executable instructions; The processor is configured to perform the method according to any one of claims 1-6.

9. An electric motor, characterized in that: Control is performed using the method described in any one of claims 1-6.

10. An electrical appliance, characterized in that: Includes the motor as described in claim 9.

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