WO2024083122A1

WO2024083122A1 - High-speed motor carrier frequency modulation method and system

Info

Publication number: WO2024083122A1
Application number: PCT/CN2023/124983
Authority: WO
Inventors: 张学锋; 白江涛
Original assignee: 势加透博洁净动力如皋有限公司
Priority date: 2022-10-17
Filing date: 2023-10-17
Publication date: 2024-04-25
Also published as: CN115347845A; CN115347845B

Abstract

The present invention relates to the technical field of motor carrier frequencies. Specifically, disclosed are a high-speed motor carrier frequency modulation method and system. The modulation method comprises the following steps: enabling all parameters to enter an initialization state after electrification; a micro-control unit obtaining an initial rotational speed of a motor by means of bus communication; and calculating a switching frequency reference value, a switching frequency maximum limit value, and a switching frequency minimum limit value corresponding to each rotational speed according to the obtained initial rotational speed of the motor. According to the present invention, for a carrier frequency, the switching frequency reference value, the switching frequency maximum limit value, and the switching frequency minimum limit value corresponding to each rotational speed are calculated according to the obtained initial rotational speed of the motor; during operation, the motor performs phase shift by means of a phase shift method of changing a switching frequency bandwidth in a dynamic frequency modulation mode and a reciprocating frequency modulation mode, the amplitude of bottom harmonic noise is also changed along with the change of the switching frequency bandwidth, and the phase shift method is one of a forward bias phase shift method, a reverse bias phase shift method, or a symmetric change phase shift method, so that electromagnetic interference is reduced, and the dependence on a common mode filter and an output filter is reduced or canceled.

Description

A high-speed motor carrier frequency modulation method and system

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on the Chinese patent application with application number 202211264202.8 and application date October 17, 2022, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into this application as a reference.

Technical Field

The invention belongs to the technical field of motor carrier frequency, and in particular relates to a high-speed motor carrier frequency modulation method and system.

Background technique

As the level of intelligence of new energy vehicle motors and electronic devices increases significantly, the electromagnetic compatibility issues between motors and electronic components are becoming increasingly severe. It has become an entry requirement for mainstream new energy vehicle manufacturers that components meet the electromagnetic compatibility Class 3 level. However, there are still some components that cannot meet the electromagnetic compatibility Class 3 requirements, especially high-voltage, high-power density, and high-frequency electrical components, such as the controller of a hydrogen fuel cell air compressor.

Summary of the invention

The present invention provides a high-speed motor carrier frequency modulation method, the modulation method steps are as follows:

S1. After power-on, all parameters enter the initialization state;

S2, the microcontroller unit obtains the initial speed of the motor through bus communication;

S3, the micro control unit calculates the switching frequency reference value, the switching frequency maximum limit value and the switching frequency minimum limit value corresponding to each speed according to the obtained initial speed of the motor;

S4, the microcontroller unit receives the speed command transmitted by the bus communication, adjusts the PWM module parameters, and the speed is adjusted accordingly. At the same time, the PWM module performs phase shifting by dynamically changing the switching frequency bandwidth through phase shifting, and the amplitude of the bottom harmonic noise also changes accordingly;

S5, the microcontroller unit determines whether the switching frequency movement reaches a limited period, and if it reaches the limited period, loads the switching frequency after dynamic frequency modulation in step S4, and if it does not reach the limited period, maintains the dynamic frequency modulation state in step S4;

S6. After loading is completed, the microcontroller receives a stop command, the motor stops running, the switching frequency changes but no stop command is received, and then returns to calculate the switching frequency corresponding to each motor speed.

Further, the phase shifting method in S4 is one of a forward bias phase shifting method, a reverse bias phase shifting method or a symmetrical phase shifting method.

Furthermore, the rotation speed and the switching frequency in S4 are adjusted in the same manner, which are either linear dynamic adjustment or dynamic step adjustment.

Furthermore, the forward bias phase shifting method is that the microcontroller unit receives the speed command transmitted by the bus communication, adjusts the module parameters, and the speed is adjusted accordingly. When the switching frequency reference value is less than half of the sum of the maximum limit value of the switching frequency and the minimum limit value of the switching frequency, the PWM module shifts the pulse waveform to the right by frequency modulation, and the switching frequency varies between the maximum limit value of the switching frequency and the minimum limit value of the switching frequency. The bandwidth of the switching frequency increases, and the amplitude of the bottom harmonic noise decreases accordingly. The bottom harmonic noise increases due to the superposition of the switching frequency bandwidth, the amplitude of the bottom harmonic noise decreases, and the EMI is also reduced accordingly.

Furthermore, the reverse bias phase shifting method is that the microcontroller unit receives the speed command transmitted by the bus communication, adjusts the module parameters, and the speed is adjusted accordingly. When the switching frequency reference value is greater than half of the sum of the maximum limit value of the switching frequency and the minimum limit value of the switching frequency, the PWM module shifts the pulse waveform to the left by frequency modulation, and the switching frequency varies between the maximum limit value of the switching frequency and the minimum limit value of the switching frequency. The switching frequency bandwidth increases, and the bottom harmonic noise amplitude decreases accordingly. The bottom harmonic noise increases due to the superposition of the switching frequency bandwidth, the bottom harmonic noise amplitude decreases, and the EMI is also reduced accordingly.

Furthermore, the symmetrical phase shifting method is that the microcontroller receives the speed command transmitted by the bus communication, adjusts the module parameters, and the speed is adjusted accordingly. When the switching frequency reference value is equal to half of the sum of the maximum limit value of the switching frequency and the minimum limit value of the switching frequency, the PWM module symmetrically shifts the pulse waveform to the left and right directions by frequency modulation. The switching frequency varies between the maximum limit value of the switching frequency and the minimum limit value of the switching frequency. The switching frequency bandwidth increases, and the bottom harmonic noise amplitude decreases accordingly. The bottom harmonic noise increases due to the superposition of the switching frequency bandwidth, and the bottom harmonic noise amplitude As the amplitude decreases, EMI also decreases.

Furthermore, the switching frequency changes between the maximum switching frequency limit value and the minimum switching frequency limit value in a reciprocating or dynamic manner.

Furthermore, the calculation formulas for the switching frequency, the maximum switching frequency limit value, and the minimum switching frequency limit value in S3 are:

Wherein, fsw is the switching frequency output per second, and N is the different preset proportional constants for respectively calculating the switching frequency reference value, the switching frequency maximum limit value, and the switching frequency minimum limit value; is the electrical frequency, n is the speed, and p is the number of motor poles.

The present invention also provides a high-speed motor carrier frequency modulation system, which includes a motor, a microcontroller and a PWM module, wherein the microcontroller is connected to the motor and the PWM module respectively, and is used to execute the above-mentioned high-speed motor carrier frequency modulation method.

Beneficial effects of the present invention: In the present invention, the carrier frequency calculates the switching frequency reference value, the switching frequency maximum limit value and the switching frequency minimum limit value corresponding to each speed according to the acquired initial speed of the motor. During the operation of the motor, the phase shifting method of changing the switching frequency bandwidth is performed by dynamic frequency modulation and reciprocating frequency modulation. The amplitude of the bottom harmonic noise also changes accordingly. The phase shifting method adopts one of the forward bias phase shifting method, the reverse bias phase shifting method or the symmetrical phase shifting method, thereby reducing electromagnetic interference, reducing or eliminating the dependence on the common mode filter and the output filter, reducing the manufacturing cost, and reducing the switching loss in the idle area by dynamic frequency modulation or reciprocating frequency modulation.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a schematic diagram of the speed and switching frequency of a high-speed motor carrier frequency modulation method;

FIG2 is a schematic diagram of switching noise harmonic reduction of a high-speed motor carrier frequency modulation method;

FIG. 3 is a process flow chart of a high-speed motor carrier frequency modulation method.

Detailed ways

The following will be combined with the drawings of the present invention specification to clearly and completely describe the technical solutions in the embodiments of the invention. 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 creative work are within the scope of protection of the present invention.

As the degree of intelligence of new energy vehicle motors and electronic devices increases significantly, the electromagnetic compatibility problem between motors and electronic components is becoming increasingly severe. It has become the entry requirement for mainstream new energy vehicle manufacturers that the components reach the electromagnetic compatibility Class 3 level. However, some components are still difficult to meet the requirements of electromagnetic compatibility Class 3, especially high-voltage, high-power density, and high-frequency electrical components, such as the controller of hydrogen fuel cell air compressor. At present, most controllers of fuel cell air compressors adopt the technical solution of two-level SiC electrical topology, which has the disadvantages of fixed switching frequency, high harmonic content, and difficulty in electromagnetic radiation suppression, making it difficult to meet the requirements of electromagnetic compatibility Class 3. At the same time, there is also low efficiency in the idle area, which cannot be further improved. Based on the current technology, in order to improve the electromagnetic compatibility performance, controller products often increase the volume and weight by adding input filters, output filters, and wrapping shielding, which makes it difficult to meet the requirements of lightweight and small size of the whole vehicle. Therefore, it is urgent to invent a high-speed motor carrier frequency modulation method.

In order to solve the above technical problems, the present invention provides a high-speed motor carrier frequency modulation method and system.

In a specific embodiment of the present invention, as shown in FIG. 1 to FIG. 3 , a high-speed motor carrier frequency modulation method is specifically disclosed, and the modulation method steps are as follows:

S1. After power-on, all parameters enter the initialization state;

S4, the microcontroller unit receives the speed command transmitted by the bus communication, adjusts the PWM module parameters, and the speed is adjusted accordingly. At the same time, the PWM module performs phase shifting by a phase shifting method that changes the switching frequency bandwidth through dynamic frequency modulation, and the amplitude of the bottom harmonic noise also changes accordingly. The phase shifting method is one of a forward bias phase shifting method, a reverse bias phase shifting method, or a symmetrical phase shifting method.

The speed and switching frequency are adjusted in the same way, either linear dynamic adjustment or dynamic step adjustment;

The PWM module is a module for pulse width modulation in the microcontroller unit;

S5, the microcontroller unit determines whether the switching frequency movement reaches a limited period, and if so, loads the switching frequency after dynamic frequency modulation in step S4, and if not, maintains the dynamic frequency modulation state in step S4;

The forward bias phase shift method is that the microcontroller unit receives the speed command transmitted by the bus communication, adjusts the module parameters, and the speed is adjusted accordingly. When the switching frequency reference value is less than half of the sum of the maximum limit value of the switching frequency and the minimum limit value of the switching frequency, the PWM module shifts the pulse waveform to the right by frequency modulation, and the switching frequency changes between the maximum limit value of the switching frequency and the minimum limit value of the switching frequency. The bandwidth of the switching frequency increases, and the amplitude of the bottom harmonic noise decreases accordingly. The bottom harmonic noise increases due to the superposition of the switching frequency bandwidth, the amplitude of the bottom harmonic noise decreases, and EMI also decreases accordingly. EMI is electromagnetic interference, which is abbreviated as EMI in the full text.

The reverse bias phase shift method is that the microcontroller unit receives the speed command transmitted by the bus communication, adjusts the module parameters, and the speed is adjusted accordingly. When the switching frequency reference value is greater than half of the sum of the maximum limit value of the switching frequency and the minimum limit value of the switching frequency, the PWM module shifts the pulse waveform to the left by frequency modulation, and the switching frequency changes between the maximum limit value of the switching frequency and the minimum limit value of the switching frequency. The switching frequency bandwidth increases, and the bottom harmonic noise amplitude decreases accordingly. The bottom harmonic noise increases due to the superposition of the switching frequency bandwidth, the bottom harmonic noise amplitude decreases, and the EMI is also reduced accordingly.

The symmetrical phase shifting method is that the microcontroller unit receives the speed command transmitted by the bus communication, adjusts the module parameters, and the speed is adjusted accordingly. When the switching frequency reference value is equal to half of the sum of the maximum limit value of the switching frequency and the minimum limit value of the switching frequency, the PWM module symmetrically shifts the pulse waveform to the left and right directions by frequency modulation. The switching frequency varies between the maximum limit value of the switching frequency and the minimum limit value of the switching frequency. The switching frequency bandwidth increases, and the bottom harmonic noise amplitude decreases accordingly. The bottom harmonic noise increases due to the superposition of the switching frequency bandwidth, the bottom harmonic noise amplitude decreases, and the EMI is also reduced accordingly.

The switching frequency varies between the maximum switching frequency limit and the minimum switching frequency limit. The change mode is reciprocating change or dynamic change.

The calculation formulas for the switching frequency, the maximum switching frequency limit value, and the minimum switching frequency limit value in S3 are:

Wherein, fsw is the switching frequency output per second, and N is different preset proportional constants when calculating the switching frequency reference value, the switching frequency maximum limit value, and the switching frequency minimum limit value respectively; is the electrical frequency, n is the speed, and p is the number of motor poles.

Embodiment 1:

In Figure 1, the horizontal axis is the motor speed, the vertical axis is the switching frequency, and the up and down arrows in Figure 1 are the states of the switching frequency changing back and forth. This formula calculates the switching frequency reference value, the switching frequency maximum limit value and the switching frequency minimum limit value output per second by the carrier frequency and each motor speed. The switching frequency reference line is formed between each switching frequency reference value; the switching frequency maximum limit line is formed between each switching frequency maximum limit value, and the switching frequency minimum limit line is formed between each switching frequency minimum limit value. The motor pole pair number p is preferably 1, and the proportional constant N when calculating the switching frequency maximum limit value corresponding to each speed of the switching frequency maximum limit line is 50; 50; the proportional constant N when calculating the switching frequency minimum limit value corresponding to each speed of the switching frequency minimum limit line is 20; the proportional constant N when calculating the switching frequency reference value corresponding to each speed of the switching frequency reference line is 30.

When the difference between the switching frequency baseline and the maximum switching frequency limit line is greater than the difference between the switching frequency baseline and the minimum switching frequency limit line, the PWM module shifts the pulse waveform to the right through dynamic frequency modulation, so that the switching frequency changes back and forth between the maximum switching frequency limit value and the minimum switching frequency limit value, thereby increasing the switching frequency bandwidth, and the amplitude of the harmonic noise decreases accordingly. The bottom harmonic noise increases due to the superposition of the switching frequency bandwidth, so that the amplitude of the bottom harmonic noise also decreases, and EMI is also reduced accordingly.

When the difference between the switching frequency baseline and the maximum switching frequency limit line is smaller than the difference between the switching frequency baseline and the minimum switching frequency limit line, the PWM module shifts the pulse waveform to the left through dynamic frequency modulation, so that the switching frequency changes back and forth between the maximum switching frequency limit value and the minimum switching frequency limit value, thereby increasing the switching frequency bandwidth, and the amplitude of the harmonic noise decreases accordingly. The bottom harmonic noise increases due to the superposition of the switching frequency bandwidth, so that the amplitude of the bottom harmonic noise also decreases, and EMI is also reduced accordingly.

When the difference between the switching frequency baseline and the switching frequency maximum limit line is equal to the switching frequency baseline When there is a gap between the switching frequency and the minimum limit line, the PWM module shifts the pulse waveform to the left and right sides through dynamic frequency modulation, so that the switching frequency changes back and forth between the maximum limit value and the minimum limit value of the switching frequency, thereby increasing the bandwidth of the switching frequency, and the amplitude of the harmonic noise decreases accordingly. The bottom harmonic noise increases due to the superposition of the switching frequency bandwidth, which reduces the amplitude of the bottom harmonic noise and reduces EMI accordingly.

When the motor runs one electrical cycle or multiple electrical cycles, the microcontroller unit determines the movement of the switching frequency. When it reaches a specified electrical cycle or multiple electrical cycles, the speed switching frequency after the above frequency modulation is loaded. After the loading is completed, the microcontroller unit receives a stop command and the motor operation ends. If the switching frequency changes but no stop command is received, it returns to calculate the switching frequency corresponding to each speed of the motor; when it does not reach the specified electrical cycle or multiple electrical cycles, the original speed switching frequency is maintained.

The X-axis in Figure 2 is the switching frequency corresponding to the harmonic, and the Y-axis is the amplitude corresponding to the harmonic; Waveform 1 in Figure 2 is the harmonic distribution under the traditional fixed switching frequency; Waveform 2 is the harmonic distribution after the harmonic is shifted by the forward bias phase shifting method using the PWM module, which makes the switching frequency bandwidth wider and the bottom harmonic noise increased, but the harmonic amplitude is greatly reduced, thereby reducing EMI.

The present invention can be applied to a two-level or three-level circuit topology with a silicon carbide power device to control the motor speed and switching frequency bandwidth, thereby reducing switching noise and electromagnetic interference.

The total loss of power devices is composed of switching loss and conduction loss. In the low-speed area, the load current is small and the conduction loss is low. Because the useful switching power is low at a fixed switching frequency, the proportion of total power device loss in the low-speed area increases, and the low-speed efficiency decreases accordingly. The switching loss can be expressed by the following formula:

Where Psw is the switching loss; E _ON is the device turn-on loss; E _OFF is the device turn-off loss; and fsw is the switching frequency. From the formula, we can see that the switching loss is related to the switching frequency. The switching frequency increases with the increase of the motor speed and decreases with the decrease of the motor speed, showing a linear change, thereby reducing the proportion of the switching loss in the low-speed area of the motor and improving the output efficiency of the low-speed area of the motor.

The embodiment of the present invention also discloses a high-speed motor carrier frequency modulation system, which includes a motor, a microcontroller and a PWM module, wherein the microcontroller is connected to the motor and the PWM module respectively, and is used to execute the high-speed motor carrier frequency modulation method of the above embodiment.

The process flow of the present invention is as follows: all parameters of the microcontroller unit enter the initialization state, and after the initialization is completed, the initial speed of the motor is obtained through bus communication, and the motor speed is calculated after receiving the obtained initial speed of the motor. The switching frequency reference value, the maximum switching frequency limit value and the minimum switching frequency limit value corresponding to each speed of the machine, the micro control unit receives the speed command transmitted by the bus communication, adjusts the PWM module parameters, and the speed is adjusted accordingly. The PWM module performs phase shifting by dynamically modulating the switching frequency bandwidth. The amplitude of the bottom harmonic noise also changes accordingly, thereby realizing dynamic frequency modulation, thereby reducing the switching loss in the idle area. The switching frequency changes dynamically or reciprocates between the maximum switching frequency limit value and the minimum switching frequency limit value, thereby reducing the electromagnetic interference capability.

The above disclosure is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

A high-speed motor carrier frequency modulation method, characterized in that the modulation method comprises the following steps:

S1. After power-on, all parameters enter the initialization state;

S2, the microcontroller unit obtains the initial speed of the motor through bus communication;

S3, the micro control unit calculates the switching frequency reference value, the switching frequency maximum limit value and the switching frequency minimum limit value corresponding to each speed according to the obtained initial speed of the motor;

S4, the microcontroller unit receives the speed command transmitted by the bus communication, adjusts the PWM module parameters, and the speed is adjusted accordingly. At the same time, the PWM module performs phase shifting by dynamically changing the switching frequency bandwidth through phase shifting, and the amplitude of the bottom harmonic noise also changes accordingly;

S5, the microcontroller unit determines whether the switching frequency movement reaches a limited period, and if it reaches the limited period, loads the switching frequency after dynamic frequency modulation in step S4, and if it does not reach the limited period, maintains the dynamic frequency modulation state in step S4;

S6. After loading is completed, the microcontroller receives a stop command, the motor stops running, the switching frequency changes but no stop command is received, and then returns to calculate the switching frequency corresponding to each motor speed.
According to a high-speed motor carrier frequency modulation method according to claim 1, it is characterized in that the phase shifting method in S4 is one of a forward bias phase shifting method, a reverse bias phase shifting method or a symmetrical change phase shifting method.
According to a high-speed motor carrier frequency modulation method according to claim 1 or 2, it is characterized in that the rotation speed and switching frequency in S4 are adjusted in the same manner, both of which are linear dynamic adjustment or dynamic step adjustment.
According to a high-speed motor carrier frequency modulation method as described in claim 2, it is characterized in that the forward bias phase shifting method is that the micro control unit receives the speed command transmitted by the bus communication, adjusts the module parameters, and the speed is adjusted accordingly. When the switching frequency reference value is less than half of the sum of the maximum limit value of the switching frequency and the minimum limit value of the switching frequency, the PWM module shifts the pulse waveform to the right by frequency modulation, and the switching frequency changes between the maximum limit value of the switching frequency and the minimum limit value of the switching frequency. The bandwidth of the switching frequency increases, and the amplitude of the bottom harmonic noise decreases accordingly. The bottom harmonic noise is increased due to the switching frequency bandwidth. The width of the signal increases due to superposition, the amplitude of the bottom harmonic noise decreases, and the EMI also decreases accordingly.
A high-speed motor carrier frequency modulation method according to claim 2, characterized in that the reverse bias phase shift method is that the microcontroller unit receives the speed command transmitted by the bus communication, adjusts the module parameters, and the speed is adjusted accordingly. When the switching frequency reference value is greater than half of the sum of the maximum limit value of the switching frequency and the minimum limit value of the switching frequency, the PWM module shifts the pulse waveform to the left by frequency modulation, and the switching frequency changes between the maximum limit value of the switching frequency and the minimum limit value of the switching frequency. The switching frequency bandwidth increases, and the bottom harmonic noise amplitude decreases accordingly. The bottom harmonic noise increases due to the superposition of the switching frequency bandwidth, the bottom harmonic noise amplitude decreases, and the EMI is also reduced accordingly.
A high-speed motor carrier frequency modulation method according to claim 2, characterized in that the symmetrical phase shifting method is that the microcontroller unit receives the speed command transmitted by the bus communication, adjusts the module parameters, and the speed is adjusted accordingly. When the switching frequency reference value is equal to half of the sum of the maximum limit value of the switching frequency and the minimum limit value of the switching frequency, the PWM module symmetrically shifts the pulse waveform to the left and right directions by frequency modulation, and the switching frequency varies between the maximum limit value of the switching frequency and the minimum limit value of the switching frequency. The switching frequency bandwidth increases, and the bottom harmonic noise amplitude decreases accordingly. The bottom harmonic noise increases due to the superposition of the switching frequency bandwidth, the bottom harmonic noise amplitude decreases, and the EMI is also reduced accordingly.
A high-speed motor carrier frequency modulation method according to claim 4, 5 or 6, characterized in that the switching frequency changes between the maximum switching frequency limit value and the minimum switching frequency limit value in a reciprocating or dynamic manner.
A high-speed motor carrier frequency modulation method according to any one of claims 1 to 7, characterized in that the calculation formula of the switching frequency reference value, the switching frequency maximum limit value and the switching frequency minimum limit value in S3 is:

Wherein, fsw is the switching frequency output per second, and N is different preset proportional constants when calculating the switching frequency reference value, the switching frequency maximum limit value, and the switching frequency minimum limit value respectively; is the electrical frequency, n is the speed, and p is the number of motor poles.
A high-speed motor carrier frequency modulation system, characterized in that it includes a motor, a microcontroller and a PWM module, wherein the microcontroller is connected to the motor and the PWM module respectively, and the microcontroller is used to execute the high-speed motor carrier frequency modulation method as described in any one of claims 1-8.