Carrier frequency control method and system based on direct current brushless motor

Abstract

The invention relates to a carrier frequency control method and system based on a direct current brushless motor, and the method comprises the steps: receiving a starting signal, and obtaining an actual rotating speed value of the direct current brushless motor through a rotating speed sensor; presetting a rotating speed threshold value, comparing the actual rotating speed value with the preset rotating speed threshold value, and adjusting the carrier frequency to be a first frequency value or a second frequency value according to a comparison result; a rising hysteresis threshold value and a falling hysteresis threshold value are preset, and the carrier frequency is prevented from being switched back and forth between the first frequency value and the second frequency value; when the carrier frequency is a second frequency value, acquiring a temperature value of the motor driving chip, and when the temperature value is higher than a temperature early warning value, further dynamically adjusting the carrier frequency; and obtaining the current carrier frequency, and adjusting the cut-off frequency and the common-mode inductance parameter of the LC filter according to the current carrier frequency, thereby optimizing the electromagnetic compatibility. According to the invention, the carrier frequency is dynamically adjusted in a grading manner, thermal management and electromagnetic compatibility design are optimized, and the balance of efficiency, noise and reliability is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a carrier frequency control method and system based on a brushless DC motor. Background Art

[0002] Brushless DC motors are widely used in many fields such as industrial automation, new energy vehicles, smart homes, etc. due to their advantages of high efficiency, energy saving, and good speed regulation performance. As a key parameter of the brushless DC motor drive system, the carrier frequency plays a vital role in the motor's operating performance.

[0003] In the brushless DC motor drive system, the choice of carrier frequency directly affects the switching loss, electromagnetic noise and thermal stability of the system. Traditional methods mostly use fixed carrier frequencies, which makes it difficult to take into account both high efficiency and low noise requirements. For example, a high carrier frequency can reduce electromagnetic noise, but will increase switching losses and temperature rise; a low carrier frequency can improve efficiency but will increase noise. The prior art lacks a method for dynamically adjusting the carrier frequency to achieve the optimal balance of system performance under different working conditions.

[0004] Therefore, it is necessary to provide a new carrier frequency control method and system based on a brushless DC motor. Summary of the invention

[0005] Based on the above problems existing in the prior art, the purpose of the embodiments of the present invention is to provide a carrier frequency control method and system based on a brushless DC motor, dynamically adjust the carrier frequency in stages, optimize thermal management and electromagnetic compatibility design, and achieve a balance between efficiency, noise and reliability.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a carrier frequency control method based on a brushless DC motor, comprising:

[0007] S1, receiving the start signal, and using the speed sensor to obtain the actual speed value of the brushless DC motor;

[0008] S2, preset a speed threshold, and compare the actual speed value with the preset speed threshold;

[0009] S3, when the actual speed value is greater than or equal to the speed threshold, the carrier frequency is set to a first frequency value; when the actual speed value is less than the speed threshold, the carrier frequency is set to a second frequency value, wherein the first frequency value is less than the second frequency value;

[0010] S4, presetting a rising hysteresis threshold and a falling hysteresis threshold to prevent the carrier frequency from switching back and forth between the first frequency value and the second frequency value;

[0011] S5, when the carrier frequency is the second frequency value, obtaining the temperature value of the motor drive chip, and when the temperature value is higher than the temperature warning, further dynamically adjusting the carrier frequency;

[0012] S6, obtaining the current carrier frequency, and adjusting the cutoff frequency and common mode inductance parameters of the LC filter according to the current carrier frequency to optimize electromagnetic compatibility.

[0013] Furthermore, in S1, the receiving of the start signal and using the speed sensor to obtain the actual speed value of the brushless DC motor include:

[0014] Step S11, after receiving the system startup instruction, the rotor speed signal of the brushless DC motor is collected in real time through a high-precision Hall speed sensor;

[0015] Step S12, using digital signal processing technology to filter the initial rotor speed signal to eliminate measurement noise caused by electromagnetic interference;

[0016] Step S13, the actual speed value is accurately calculated by the built-in PWM capture unit of the microcontroller, and the sampling frequency is set to 1kHz.

[0017] Further, in S4, the preset rising hysteresis threshold and the falling hysteresis threshold prevent the carrier frequency from switching back and forth between the first frequency value and the second frequency value, including:

[0018] Step S41, presetting a rising hysteresis threshold, when the actual speed value is greater than the sum of the speed threshold and the rising hysteresis threshold, switching the carrier frequency mode from the second frequency value to the first frequency value;

[0019] Step S42, preset a falling hysteresis threshold, and when the actual speed threshold is less than the difference between the preset speed threshold and the falling hysteresis threshold, switch the carrier frequency mode from the first frequency value to the second frequency value;

[0020] Step S43, using a state latch register to maintain the current mode for at least 200ms to prevent erroneous switching due to instantaneous speed fluctuations.

[0021] Further, the rising hysteresis threshold ΔH is set to 2% of the speed threshold N0, that is, ΔH=2%N0. When N>(N0+2%N0), the carrier frequency mode is switched from the second frequency value F2 to the first frequency value F1. The mode switching is performed only when the actual speed value N significantly exceeds the speed threshold N0 by a certain amplitude.

[0022] The falling hysteresis threshold ΔL is set to 3% of the speed threshold N0, that is, ΔL=3%N0. When N<(N0+3%N0), the carrier frequency mode is switched from the first frequency value F1 to the second frequency value F2. The mode switching will only be performed when the actual speed value N is significantly lower than the speed threshold N0 by a certain amplitude.

[0023] Further, in S5, when the carrier frequency is the second frequency value, the temperature value of the motor driver chip is obtained, and when the temperature value is higher than the temperature warning, the carrier frequency is further dynamically adjusted, including:

[0024] Step S51, when the carrier frequency is a second frequency value, obtaining a real-time temperature value of the motor driver chip through a temperature sensor, and monitoring the junction temperature of the motor driver chip in real time;

[0025] Step S52, when the real-time temperature value of the motor drive chip is greater than or equal to the first temperature threshold, adopting the first-level early warning protection, including: starting the dynamic frequency modulation algorithm, reducing the carrier frequency at a slope of 0.1kHz / °C;

[0026] Step S53, when the real-time temperature value of the motor driving chip is greater than or equal to the second temperature threshold, a secondary protection measure is adopted, including: forcibly switching the forced carrier frequency mode to the first frequency value and triggering an over-temperature interrupt;

[0027] Step S54, when the real-time temperature value of the motor driver chip is greater than or equal to the third temperature threshold, a three-level shutdown protection is adopted, including: immediately shutting down the PWM output and activating the hardware watchdog; wherein the first temperature threshold < the second temperature threshold < the third temperature threshold.

[0028] Further, adjusting the cutoff frequency of the LC filter according to the current carrier frequency includes:

[0029] The cutoff frequency of the LC filter is calculated as:

[0030]

[0031] Among them, f c is the cut-off frequency, L is the inductance, and C is the capacitance;

[0032] According to the current carrier frequency f0, set the cutoff frequency f c =0.3×f0, thus ensuring effective filtering of switching harmonics;

[0033] When the carrier frequency f0 is the first frequency value, that is, the current carrier frequency f0 = 8 kHz, the inductance L is selected to be 100 μH, the capacitance C is selected to be 0.47 μF, and the cut-off frequency f0 is about 2.4 kHz;

[0034] When the carrier frequency f0 is the second frequency value, that is, the current carrier frequency f0 = 16 kHz, the inductance L is selected to be 47 μH, the capacitance C is selected to be 0.22 μF, and the cut-off frequency f0 is about 4.8 kHz;

[0035] According to the current carrier frequency, different inductance / capacitance combinations are switched through relays, or the equivalent value of inductance / capacitance is adjusted using a digital potentiometer;

[0036] Further, adjusting the common mode inductance parameters according to the current carrier frequency includes:

[0037] The impedance calculation formula of common mode inductor is:

[0038] Z cm =2πf n L cm

[0039] Among them, Z cm is the impedance of the common mode inductor, f n is the noise frequency, L cm is the common mode inductance value;

[0040] The inductance level is switched according to the current carrier frequency. When the carrier frequency f0 is the first frequency value, that is, when the current carrier frequency f0 = 8 kHz, the common mode inductance value L is used. cm =10mH to suppress low-frequency common-mode noise; when the carrier frequency f0 is the second frequency value, that is, when the current carrier frequency f0 = 16kHZ, the common-mode inductance value L is used cm =4.7mH to optimize high frequency attenuation.

[0041] A carrier frequency control system based on a brushless DC motor is applied to the above-mentioned carrier frequency control method based on a brushless DC motor, and the system comprises:

[0042] The speed acquisition module is used to receive the start signal and use the speed sensor to obtain the actual speed value of the brushless DC motor;

[0043] A speed threshold determination module is used to preset a speed threshold and compare the actual speed value with the preset speed threshold;

[0044] A carrier frequency control module, used to set the carrier frequency to a first frequency value when the actual speed value is greater than or equal to the speed threshold; and to set the carrier frequency to a second frequency value when the actual speed value is less than the speed threshold, wherein the first frequency value is less than the second frequency value;

[0045] A hysteresis anti-oscillation processing module is used to preset a rising hysteresis threshold and a falling hysteresis threshold to prevent the carrier frequency from switching back and forth between a first frequency value and a second frequency value;

[0046] A temperature protection module, used for obtaining the temperature value of the motor driver chip when the carrier frequency is a second frequency value, and further dynamically adjusting the carrier frequency when the temperature value is higher than the temperature warning value;

[0047] The electromagnetic compatibility optimization module is used to obtain the current carrier frequency and adjust the cutoff frequency and common mode inductance parameters of the LC filter according to the current carrier frequency to optimize the electromagnetic compatibility.

[0048] The embodiment of the present invention further provides a network side server, including:

[0049] At least one processor; and a memory connected to the at least one processor in communication; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the above-mentioned carrier frequency control method based on the brushless DC motor.

[0050] The embodiment of the present invention further provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the above-mentioned carrier frequency control method based on a brushless DC motor is implemented.

[0051] The beneficial effects of the present invention are as follows: the carrier frequency control method based on a brushless DC motor of the present invention comprises receiving a start signal, using a speed sensor to obtain an actual speed value of the brushless DC motor; presetting a speed threshold, and comparing the actual speed value with the preset speed threshold; when the actual speed value is greater than or equal to the speed threshold, setting the carrier frequency to a first frequency value; when the actual speed value is less than the speed threshold, setting the carrier frequency to a second frequency value, wherein the first frequency value is less than the second frequency value; presetting a rising hysteresis threshold and a falling hysteresis threshold to avoid the carrier frequency from switching back and forth between the first frequency value and the second frequency value; when the carrier frequency is the second frequency value, obtaining the temperature value of the motor drive chip, and when the temperature value is higher than the temperature warning, further dynamically adjusting the carrier frequency; obtaining the current carrier frequency, and adjusting the cutoff frequency and common-mode inductance parameters of the LC filter according to the current carrier frequency to optimize electromagnetic compatibility. The carrier frequency control method based on the brushless DC motor of the present invention achieves a balance between efficiency, noise and reliability by dynamically adjusting the carrier frequency in stages, optimizing thermal management and electromagnetic compatibility design; the carrier frequency control method switches the carrier frequency based on a speed threshold and a hysteresis loop mechanism, and combines high-performance heat dissipation design and an adaptive algorithm to significantly reduce noise and temperature rise, and is suitable for high-demand motor drive scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0053] In the figure:

[0054] Figure 1A flow chart of a carrier frequency control method based on a brushless DC motor provided in Embodiment 1 of the present invention;

[0055] Figure 2 A schematic diagram of a module of a carrier frequency control system based on a brushless DC motor provided in the second embodiment of the present invention;

[0056] Figure 3 It is a structural diagram of a network-side server provided according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0058] First embodiment:

[0059] The first embodiment of the present invention provides a carrier frequency control method based on a brushless DC motor, including: receiving a start signal, using a speed sensor to obtain the actual speed value of the brushless DC motor; presetting a speed threshold, and comparing the actual speed value with the preset speed threshold; when the actual speed value is greater than or equal to the speed threshold, setting the carrier frequency to a first frequency value; when the actual speed value is less than the speed threshold, setting the carrier frequency to a second frequency value, wherein the first frequency value is less than the second frequency value; presetting a rising hysteresis threshold and a falling hysteresis threshold to avoid the carrier frequency from switching back and forth between the first frequency value and the second frequency value; when the carrier frequency is the second frequency value, obtaining the temperature value of the motor drive chip, and when the temperature value is higher than the temperature warning, further dynamically adjusting the carrier frequency; obtaining the current carrier frequency, and adjusting the cutoff frequency and common mode inductance parameters of the LC filter according to the current carrier frequency to optimize electromagnetic compatibility. The carrier frequency control method based on the brushless DC motor of the present invention achieves a balance between efficiency, noise and reliability by dynamically adjusting the carrier frequency in stages, optimizing thermal management and electromagnetic compatibility design; the carrier frequency control method switches the carrier frequency based on a speed threshold and a hysteresis loop mechanism, and combines high-performance heat dissipation design and an adaptive algorithm to significantly reduce noise and temperature rise, and is suitable for high-demand motor drive scenarios.

[0060] The following is a detailed description of the implementation details of the carrier frequency control method based on the brushless DC motor in this embodiment. The following content is only for the convenience of understanding the implementation details, which is not necessary for the implementation of this solution. The specific process of this embodiment is as follows: Figure 1 As shown, this embodiment is applied to a carrier frequency control system based on a brushless DC motor.

[0061] Step S1: Receive a start signal and obtain the actual rotational speed value of the DC brushless motor using a rotational speed sensor.

[0062] Specifically, the steps of receiving the start signal and obtaining the motor rotational speed of the DC brushless motor using a rotational speed sensor include the following steps:

[0063] Step S11: When a system start instruction is received, the rotational speed signal of the rotor of the DC brushless motor is collected in real time through a high-precision Hall rotational speed sensor.

[0064] Specifically, a high-precision Hall effect rotational speed sensor is used to detect the magnetic field change of the rotor permanent magnet through a magnetosensitive element. The sensor is installed on the stator side of the motor, maintaining an air gap of 1 - 3 mm from the rotor poles to ensure that the magnetic flux change can be sensitively captured. The output of the sensor is a digital square wave signal, and each pulse corresponds to one pass of the rotor poles.

[0065] Step S12: Use digital signal processing technology to filter the initial rotor rotational speed signal to eliminate measurement noise caused by electromagnetic interference.

[0066] Step S13: Accurately calculate the actual rotational speed value through the PWM capture unit built into the microcontroller, and set the sampling frequency to 1 kHz.

[0067] Step S2: Preset a rotational speed threshold and compare the actual rotational speed value with the preset rotational speed threshold.

[0068] Specifically, the rotational speed threshold can be set by the system before leaving the factory, manually input by the user, or through remote control technologies such as the Internet of Things platform, Bluetooth, Wi-Fi, etc. Managers or technicians can send instructions from a place far away from the device to set the preset rotational speed threshold. Subsequently, the actual rotational speed value N is numerically compared with the preset rotational speed threshold N0.

[0069] As an example, the rotational speed threshold N0 is set to 1500 rpm.

[0070] Step S3: When the actual rotational speed value is greater than or equal to the rotational speed threshold, set the carrier frequency to a first frequency value; when the actual rotational speed value is less than the rotational speed threshold, set the carrier frequency to a second frequency value, where the first frequency value is less than the second frequency value.

[0071] Specifically, when the actual rotational speed value N is greater than or equal to the rotational speed threshold N0, i.e., N ≥ N0, set the carrier frequency to the first frequency value F1; when the actual rotational speed value N is less than the rotational speed threshold N0, i.e., N < N0, set the carrier frequency to the second frequency value F2; since the first frequency value F1 is less than the second frequency value F2, i.e., F1 < F2.

[0072] That is to say, when the actual speed value N is a high speed, that is, the actual speed value N is greater than or equal to the speed threshold value N0, a low carrier frequency, that is, the first frequency value F1, is used. At this time, the switching loss is reduced by reducing the number of IGBT switches, thereby improving the system efficiency. At this time, due to the reduction in switching losses, the temperature rise of the motor components is lower than that at high carrier frequencies, and the wind noise at high motor speeds can cover the electromagnetic sound. When the actual speed value N is a low speed, that is, the actual speed value N is less than the speed threshold value N0, a high carrier frequency, that is, the second frequency value F2, is used. The high-frequency carrier can more accurately control the current and voltage of the motor, reduce the current fluctuations and instability, thereby effectively reducing the electromagnetic force fluctuations caused by current changes, thereby reducing electromagnetic noise.

[0073] As an example, the first frequency value F1 is 8 KHz, and the second frequency value F2 is 16 KHz.

[0074] Step S4, presetting a rising hysteresis threshold and a falling hysteresis threshold to prevent the carrier frequency from switching back and forth between the first frequency value and the second frequency value.

[0075] Specifically, the preset rising hysteresis threshold and the falling hysteresis threshold to prevent the carrier frequency from switching back and forth between the first frequency value and the second frequency value include the following steps:

[0076] Step S41, preset a rising hysteresis threshold, when the actual speed value is greater than the sum of the speed threshold and the rising hysteresis threshold, switch the carrier frequency mode from the second frequency value to the first frequency value.

[0077] Specifically, a rising hysteresis threshold ΔH is preset, and the rising hysteresis threshold ΔH is used to determine whether to switch the carrier frequency mode. When the actual speed value N is greater than the sum of the speed threshold N0 and the rising hysteresis threshold ΔH, that is, N>(N0+ΔH), the carrier frequency mode is switched from the second frequency value F2 to the first frequency value F1.

[0078] The rising hysteresis threshold ΔH is set to 2% of the speed threshold N0, that is, ΔH=2%N0, that is, when N>(N0+2%N0), the carrier frequency mode is switched from the second frequency value F2 to the first frequency value F1. The mode switching is performed only when the actual speed value N significantly exceeds the speed threshold N0 by a certain amplitude, thereby avoiding the erroneous switching caused by the small fluctuation of the actual speed value N near the speed threshold N0.

[0079] Step S42, preset a falling hysteresis threshold, when the actual speed threshold is less than the difference between the preset speed threshold and the falling hysteresis threshold, switch the carrier frequency mode from the first frequency value to the second frequency value.

[0080] Specifically, a descending hysteresis threshold ΔL is preset, and the descending hysteresis threshold ΔL is used to determine whether to switch the carrier frequency mode. When the actual speed value N is less than the difference between the speed threshold N0 and the descending hysteresis threshold ΔL, that is, N<(N0+ΔH), the carrier frequency mode is switched from the first frequency value F1 to the second frequency value F2.

[0081] Among them, the falling hysteresis threshold ΔL is set to 3% of the speed threshold N0, that is, ΔL=3%N0, that is, when N<(N0+3%N0), the carrier frequency mode is switched from the first frequency value F1 to the second frequency value F2. Only when the actual speed value N is significantly lower than the speed threshold N0 by a certain amplitude, the mode switching will be performed, avoiding the false switching caused by the small fluctuation of the actual speed value N near the speed threshold N0, and further enhancing the stability of the system. .

[0082] Step S43, using a state latch register to maintain the current mode for at least 200ms to prevent erroneous switching due to instantaneous speed fluctuations.

[0083] Specifically, the state latch register is used to lock the current carrier frequency mode. The state latch register can record the current carrier frequency mode of the motor. The motor must maintain the current carrier frequency mode for at least 200ms to prevent false switching caused by instantaneous speed fluctuations.

[0084] In actual operation, the motor speed may fluctuate briefly due to instantaneous changes in load, etc. If there is no limit on the hold time, the system may frequently switch modes, affecting the normal operation of the system. By setting a hold time of at least 200ms, it is possible to filter out instantaneous interference caused by special circumstances, ensuring that the system runs in a relatively stable state, thereby improving the stability and reliability of the system.

[0085] Step S5, when the carrier frequency is a second frequency value, the temperature value of the motor drive chip is obtained, and when the temperature value is higher than the temperature warning, the carrier frequency is further dynamically adjusted.

[0086] Specifically, when the carrier frequency is the second frequency value, obtaining the real-time temperature value of the motor driver chip, and when the real-time temperature value is higher than the temperature warning, further dynamically adjusting the carrier frequency includes the following steps:

[0087] Step S51, when the carrier frequency is a second frequency value, the real-time temperature value of the motor driver chip is obtained through the temperature sensor, and the junction temperature of the motor driver chip is monitored in real time.

[0088] Specifically, when the second frequency value is the high carrier frequency mode, the junction temperature of the motor driver chip is monitored in real time through the temperature sensor integrated on the motor driver chip. Since the workload of the motor driver chip is relatively large in the high carrier frequency mode, the switching loss is larger than that at the low carrier frequency, and the temperature rise of the motor device is higher than that at the low carrier frequency, the heating of the motor driver chip may be more serious, so temperature monitoring is required to ensure the safe and stable operation of the system.

[0089] Step S52, when the real-time temperature value of the motor drive chip is greater than or equal to the first temperature threshold, a first-level early warning protection is adopted, including: starting a dynamic frequency modulation algorithm and reducing the carrier frequency at a slope of 0.1kHz / °C.

[0090] Specifically, when the real-time temperature value T of the motor driver chip is greater than or equal to the first temperature threshold T1, the system enters a first-level warning state. The first temperature threshold T1 is pre-set based on the normal operating temperature range and performance characteristics of the driver chip. When the first temperature threshold T1 is reached, it means that the driver chip has begun to show signs of overheating, and certain measures need to be taken to reduce the temperature.

[0091] Start the dynamic frequency modulation algorithm and reduce the carrier frequency at a slope of 0.1kHz / ℃. Reducing the carrier frequency can reduce the switching loss of the chip, thereby reducing the heat generated by the chip. As the temperature rises, the carrier frequency will gradually decrease at a fixed slope to dynamically adapt to the temperature changes of the chip, alleviating the overheating problem of the chip to a certain extent.

[0092] Step S53, when the real-time temperature value of the motor driving chip is greater than or equal to the second temperature threshold, a secondary protection measure is adopted, including: forcibly switching the forced carrier frequency mode to the first frequency value and triggering an over-temperature interrupt.

[0093] Specifically, when the real-time temperature value T of the motor driver chip is greater than or equal to the second temperature threshold T2, the system enters the secondary protection state. At this time, the temperature of the motor driver chip is already high. If more powerful measures are not taken, the chip may be damaged.

[0094] On the one hand, the carrier frequency mode is forced to be switched to the low carrier frequency mode of the first frequency value. In the low carrier frequency mode, the switching times of the chip are reduced, the switching loss is reduced, and the heat generation can be effectively reduced. On the other hand, an over-temperature interrupt is triggered to notify the system software to perform corresponding processing, such as recording over-temperature events and taking other auxiliary heat dissipation measures, so as to ensure the safety of the system.

[0095] Step S54, when the real-time temperature value of the motor driver chip is greater than or equal to the third temperature threshold, a three-level shutdown protection is adopted, including: immediately shutting down the PWM output and activating the hardware watchdog, wherein the first temperature threshold < the second temperature threshold < the third temperature threshold.

[0096] Specifically, when the real-time temperature value T of the motor driver chip is greater than or equal to the third temperature threshold T3, the system enters the third-level shutdown state. The third temperature threshold T3 is the higher temperature that the motor driver chip can withstand. At this time, the motor driver chip is already in a very dangerous state, and continued operation may cause permanent damage.

[0097] At this time, immediately turn off the PWM (pulse width modulation) output, stop providing the driving signal to the driver chip, and stop the chip from working, thereby avoiding further heating; at the same time, activate the hardware watchdog, which can perform a reset operation when an abnormality occurs in the system, ensuring that the system can restart normally after the overheating fault is eliminated, thereby ensuring the reliability and stability of the system.

[0098] Furthermore, the first temperature threshold T1<the second temperature threshold T2<the third temperature threshold T3, that is, T1 <T2<T3。

[0099] By setting three-level protection measures for different real-time temperature values ​​T of the driver chip, the system can gradually take corresponding protection actions according to temperature changes to avoid chip damage due to overheating, further ensuring the reliability and stability of the system.

[0100] As an example, the first temperature threshold T1 is 65°C, the second temperature threshold T2 is 80°C, and the third temperature threshold T3 is 100°C.

[0101] Step S6, obtaining the current carrier frequency, and adjusting the cutoff frequency and common mode inductance parameters of the LC filter according to the current carrier frequency to optimize electromagnetic compatibility.

[0102] Specifically, adjusting the cutoff frequency of the LC filter according to the current carrier frequency includes:

[0103] The cutoff frequency of the LC filter is calculated as:

[0104]

[0105] Among them, f c is the cut-off frequency, L is the inductance, and C is the capacitance.

[0106] According to the current carrier frequency f0, set the cutoff frequency f c =0.3×f0, thereby ensuring effective filtering of switching harmonics.

[0107] When the carrier frequency f0 is the first frequency value, that is, the current carrier frequency f0=8 kHz, the inductance L is selected to be 100 μH, and the capacitance C is selected to be 0.47 μF. At this time, the cut-off frequency f0 is approximately 2.4 kHz.

[0108] When the carrier frequency f0 is the second frequency value, that is, the current carrier frequency f0=16 kHz, the inductance L is selected to be 47 μH, and the capacitance C is selected to be 0.22 μF. At this time, the cut-off frequency f0 is approximately 4.8 kHz.

[0109] Different inductance / capacitance combinations are switched through relays according to the current carrier frequency, or the inductance / capacitance equivalent value is adjusted using a digital potentiometer.

[0110] The adjusting the common mode inductance parameters according to the current carrier frequency includes:

[0111] The impedance calculation formula of common mode inductor is:

[0112] Z cm =2πf n L cm

[0113] Among them, Z cm is the impedance of the common mode inductor, f n is the noise frequency, L cm is the common mode inductance value.

[0114] The inductance level is switched according to the current carrier frequency. When the carrier frequency f0 is the first frequency value, that is, when the current carrier frequency f0 = 8 kHz, the common mode inductance value L is used. cm =10mH to suppress low-frequency common-mode noise; when the carrier frequency f0 is the second frequency value, that is, when the current carrier frequency f0 = 16kHZ, the common-mode inductance value L is used cm =4.7mH to optimize high frequency attenuation.

[0115] Furthermore, the common mode inductor uses a laminated ferrite inductor with a core saturation current greater than 5A, in order to avoid degradation of the inductor performance under high current conditions.

[0116] The first embodiment of the present invention provides a carrier frequency control method based on a brushless DC motor, including receiving a start signal, using a speed sensor to obtain an actual speed value of the brushless DC motor; presetting a speed threshold, and comparing the actual speed value with the preset speed threshold; when the actual speed value is greater than or equal to the speed threshold, setting the carrier frequency to a first frequency value; when the actual speed value is less than the speed threshold, setting the carrier frequency to a second frequency value, wherein the first frequency value is less than the second frequency value; presetting a rising hysteresis threshold and a falling hysteresis threshold to avoid the carrier frequency from switching back and forth between the first frequency value and the second frequency value; when the carrier frequency is the second frequency value, obtaining the temperature value of the motor drive chip, and when the temperature value is higher than the temperature warning, further dynamically adjusting the carrier frequency; obtaining the current carrier frequency, and adjusting the cutoff frequency and common-mode inductance parameters of the LC filter according to the current carrier frequency to optimize electromagnetic compatibility. The carrier frequency control method based on the brushless DC motor of the present invention achieves a balance between efficiency, noise and reliability by dynamically adjusting the carrier frequency in stages, optimizing thermal management and electromagnetic compatibility design; the carrier frequency control method switches the carrier frequency based on a speed threshold and a hysteresis loop mechanism, and combines high-performance heat dissipation design and an adaptive algorithm to significantly reduce noise and temperature rise, and is suitable for high-demand motor drive scenarios.

[0117] Second implementation method:

[0118] like Figure 2 As shown, the second embodiment of the present invention provides a carrier frequency control system based on a brushless DC motor, the system comprising: a speed acquisition module 201, a speed threshold determination module 202, a carrier frequency control module 203, a hysteresis anti-oscillation processing module 204, a temperature protection module 205, and an electromagnetic compatibility optimization module 206.

[0119] Specifically, the speed acquisition module 201 is used to receive a start signal and use a speed sensor to obtain the actual speed value of the DC brushless motor; the speed threshold determination module 202 is used to preset a speed threshold and compare the actual speed value with the preset speed threshold; the carrier frequency control module 203 is used to set the carrier frequency to a first frequency value when the actual speed value is greater than or equal to the speed threshold; when the actual speed value is less than the speed threshold, the carrier frequency is set to a second frequency value, wherein the first frequency value is less than the second frequency value; the hysteresis anti-oscillation processing module 204 is used to preset a rising hysteresis threshold and a falling hysteresis threshold to avoid the carrier frequency switching back and forth between the first frequency value and the second frequency value; the temperature protection module 205 is used to obtain the temperature value of the motor drive chip when the carrier frequency is the second frequency value, and further dynamically adjust the carrier frequency when the temperature value is higher than the temperature warning; the electromagnetic compatibility optimization module 206 is used to obtain the current carrier frequency, and adjust the cutoff frequency and common mode inductance parameters of the LC filter according to the current carrier frequency to optimize the electromagnetic compatibility.

[0120] It is not difficult to find that this embodiment is a system embodiment corresponding to the first embodiment, and this embodiment can be implemented in conjunction with the first embodiment. The relevant technical details mentioned in the first embodiment are still valid in this embodiment, and in order to reduce repetition, they are not repeated here. Accordingly, the relevant technical details mentioned in this embodiment can also be applied in the first embodiment.

[0121] It is worth mentioning that all modules involved in this embodiment are logic modules. In practical applications, a logic unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. In addition, in order to highlight the innovative part of the present invention, this embodiment does not introduce units that are not closely related to solving the technical problem proposed by the present invention, but this does not mean that there are no other units in this embodiment.

[0122] A third embodiment of the present invention relates to a network side server, such as Figure 3 As shown, it includes at least one processor 302; and a memory 301 that is communicatively connected to the at least one processor 302; wherein the memory 301 stores instructions that can be executed by the at least one processor 302, and the instructions are executed by the at least one processor 302 so that the at least one processor 302 can execute the above-mentioned data processing method.

[0123] The memory 301 and the processor 302 are connected in a bus manner, and the bus may include any number of interconnected buses and bridges, and the bus connects various circuits of one or more processors 302 and the memory 301 together. The bus can also connect various other circuits such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and are therefore not further described herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be one element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices on a transmission medium. The data processed by the processor 302 is transmitted on a wireless medium via an antenna, and further, the antenna also receives data and transmits the data to the processor 302.

[0124] The processor 302 is responsible for managing the bus and general processing, and can also provide various functions, including timing, peripheral interfaces, voltage regulation, power management and other control functions. The memory 301 can be used to store data used by the processor 302 when performing operations.

[0125] The fourth embodiment of the present invention relates to a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the carrier frequency control method based on a brushless DC motor in the first embodiment is implemented.

[0126] That is, those skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including several instructions to enable a device (which can be a single-chip microcomputer, chip, etc.) or a processor to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0127] The above is only an embodiment of the present invention. The common sense such as the known specific structure and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field of the invention before the application date or priority date, can know all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the scope of protection of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A carrier frequency control method based on a brushless DC motor, characterized in that: include: S1, receiving the start signal, and using the speed sensor to obtain the actual speed value of the brushless DC motor; S2, preset a speed threshold, and compare the actual speed value with the preset speed threshold; S3, when the actual speed value is greater than or equal to the speed threshold, the carrier frequency is set to a first frequency value; when the actual speed value is less than the speed threshold, the carrier frequency is set to a second frequency value, wherein the first frequency value is less than the second frequency value; S4, presetting a rising hysteresis threshold and a falling hysteresis threshold to prevent the carrier frequency from switching back and forth between the first frequency value and the second frequency value; S5, when the carrier frequency is the second frequency value, obtaining the temperature value of the motor drive chip, and when the temperature value is higher than the temperature warning, further dynamically adjusting the carrier frequency; S6, obtaining the current carrier frequency, and adjusting the cutoff frequency and common mode inductance parameters of the LC filter according to the current carrier frequency to optimize electromagnetic compatibility.

2. The carrier frequency control method based on a brushless DC motor according to claim 1, characterized in that: In S1, the receiving of the start signal and using the speed sensor to obtain the actual speed value of the brushless DC motor include: Step S11, after receiving the system startup instruction, the rotor speed signal of the brushless DC motor is collected in real time through a high-precision Hall speed sensor; Step S12, using digital signal processing technology to filter the initial rotor speed signal to eliminate measurement noise caused by electromagnetic interference; Step S13, the actual speed value is accurately calculated by the built-in PWM capture unit of the microcontroller, and the sampling frequency is set to 1kHz.

3. The carrier frequency control method based on a brushless DC motor according to claim 1, characterized in that: In S4, the preset rising hysteresis threshold and the falling hysteresis threshold prevent the carrier frequency from switching back and forth between the first frequency value and the second frequency value, including: Step S41, presetting a rising hysteresis threshold, when the actual speed value is greater than the sum of the speed threshold and the rising hysteresis threshold, switching the carrier frequency mode from the second frequency value to the first frequency value; Step S42, preset a falling hysteresis threshold, and when the actual speed threshold is less than the difference between the preset speed threshold and the falling hysteresis threshold, switch the carrier frequency mode from the first frequency value to the second frequency value; Step S43, using a state latch register to maintain the current mode for at least 200ms to prevent erroneous switching due to instantaneous speed fluctuations.

4. The carrier frequency control method based on a brushless DC motor according to claim 3, characterized in that: The rising hysteresis threshold ΔH is set to 2% of the speed threshold N0, that is, ΔH=2%N0. When N>(N0+2%N0), the carrier frequency mode is switched from the second frequency value F2 to the first frequency value F1. The mode switching is performed only when the actual speed value N significantly exceeds the speed threshold N0 by a certain amplitude. The falling hysteresis threshold ΔL is set to 3% of the speed threshold N0, that is, ΔL=3%N0. When N<(N0+3%N0), the carrier frequency mode is switched from the first frequency value F1 to the second frequency value F2. The mode switching will only be performed when the actual speed value N is significantly lower than the speed threshold N0 by a certain amplitude.

5. The carrier frequency control method based on a brushless DC motor according to claim 1, characterized in that: In S5, when the carrier frequency is the second frequency value, the temperature value of the motor driver chip is obtained, and when the temperature value is higher than the temperature warning, the carrier frequency is further dynamically adjusted, including: Step S51, when the carrier frequency is a second frequency value, obtaining a real-time temperature value of the motor driver chip through a temperature sensor, and monitoring the junction temperature of the motor driver chip in real time; Step S52, when the real-time temperature value of the motor drive chip is greater than or equal to the first temperature threshold, adopting the first-level early warning protection, including: starting the dynamic frequency modulation algorithm, reducing the carrier frequency at a slope of 0.1kHz / °C; Step S53, when the real-time temperature value of the motor driving chip is greater than or equal to the second temperature threshold, a secondary protection measure is adopted, including: forcibly switching the forced carrier frequency mode to the first frequency value and triggering an over-temperature interrupt; Step S54, when the real-time temperature value of the motor driver chip is greater than or equal to the third temperature threshold, a three-level shutdown protection is adopted, including: immediately shutting down the PWM output and activating the hardware watchdog; wherein the first temperature threshold < the second temperature threshold < the third temperature threshold.

6. The carrier frequency control method based on a brushless DC motor according to claim 1, characterized in that: The step of adjusting the cutoff frequency of the LC filter according to the current carrier frequency includes: The cutoff frequency of the LC filter is calculated as: Among them, f c is the cut-off frequency, L is the inductance, and C is the capacitance; According to the current carrier frequency f0, set the cutoff frequency f c =0.3×f0, thus ensuring effective filtering of switching harmonics; When the carrier frequency f0 is the first frequency value, that is, the current carrier frequency f0 = 8 kHz, the inductance L is selected to be 100 μH, the capacitance C is selected to be 0.47 μF, and the cut-off frequency f0 is about 2.4 kHz; When the carrier frequency f0 is the second frequency value, that is, the current carrier frequency f0 = 16 kHz, the inductance L is selected to be 47 μH, the capacitance C is selected to be 0.22 μF, and the cut-off frequency f0 is about 4.8 kHz; According to the current carrier frequency, different inductance / capacitance combinations are switched through relays, or the equivalent value of inductance / capacitance is adjusted using a digital potentiometer; 7. The carrier frequency control method based on a brushless DC motor according to claim 1, characterized in that: The adjusting the common mode inductance parameters according to the current carrier frequency includes: The impedance calculation formula of common mode inductor is: WITH cm =2πf n L cm Among them, Z cm is the impedance of the common mode inductor, f n is the noise frequency, L cm is the common mode inductance value; The inductance level is switched according to the current carrier frequency. When the carrier frequency f0 is the first frequency value, that is, when the current carrier frequency f0 = 8 kHz, the common mode inductance value L is used. cm =10mH to suppress low-frequency common-mode noise; when the carrier frequency f0 is the second frequency value, that is, when the current carrier frequency f0 = 16kHZ, the common-mode inductance value L is used cm =4.7mH to optimize high frequency attenuation.

8. A carrier frequency control system based on a brushless DC motor, characterized in that: The carrier frequency control method based on the brushless DC motor described in claims 1-7 is applied to the system comprising: The speed acquisition module is used to receive the start signal and use the speed sensor to obtain the actual speed value of the brushless DC motor; A speed threshold determination module is used to preset a speed threshold and compare the actual speed value with the preset speed threshold; A carrier frequency control module, used to set the carrier frequency to a first frequency value when the actual speed value is greater than or equal to the speed threshold; and to set the carrier frequency to a second frequency value when the actual speed value is less than the speed threshold, wherein the first frequency value is less than the second frequency value; A hysteresis anti-oscillation processing module is used to preset a rising hysteresis threshold and a falling hysteresis threshold to prevent the carrier frequency from switching back and forth between a first frequency value and a second frequency value; A temperature protection module, used for obtaining the temperature value of the motor drive chip when the carrier frequency is a second frequency value, and further dynamically adjusting the carrier frequency when the temperature value is higher than the temperature warning value; The electromagnetic compatibility optimization module is used to obtain the current carrier frequency and adjust the cutoff frequency and common mode inductance parameters of the LC filter according to the current carrier frequency to optimize the electromagnetic compatibility.

9. A network side server, characterized in that: include: at least one processor; as well as, a memory communicatively connected to the at least one processor; wherein, The memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the carrier frequency control method based on a brushless DC motor as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the carrier frequency control method based on a brushless DC motor according to any one of claims 1 to 7 is implemented.

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