Method based on segmented synchronous SVPWM

Abstract

The present invention provides a method based on segmented synchronous SVPWM, including: determining the required modulation index; obtaining the stator frequency, the division number of the previous modulation period, and the actual execution angle interval; judging whether to switch frequencies according to the required modulation index, the stator frequency, and the actual execution angle interval; and when switching frequencies, determining the division number of this period, and determining the sampling angle according to the division number of this period; correcting the required modulation index according to the division number to obtain the corrected modulation index; calculating the first and second modulation periods of this period according to the division number and the stator frequency; calculating the comparison value at the sampling angle according to the first and second modulation periods, the sampling angle, and the corrected modulation index; determining the angles of the three-phase pulse switching angles of this period according to the comparison value; determining the initial levels of the three-phase pulses according to the vector at the initial moment of this period; and sending the first modulation period, the angles of the three-phase pulse switching angles, and the initial levels to the second processor for pulse control by the second processor.

Description

Technical Field

[0001] The present invention relates to the technical field of digital signal processing, and particularly to a method based on segmented synchronous space vector pulse width modulation (SVPWM). Background Art

[0002] For high-power traction drive systems such as electric locomotives and subways, the switching devices have relatively large losses, but the heat dissipation capacity of the power module is limited, and the maximum switching frequency is usually limited within a few hundred hertz. In order to improve the symmetry of the output voltage in the medium and high speed stages and reduce the current harmonic distortion, a synchronous modulation method is usually adopted.

[0003] For the purpose of energy conservation, weight reduction, noise reduction, cost reduction, and improving the service life of key devices, compared with the past, the temperature rise margin of the traction motor is reduced due to volume and weight limitations; the electromagnetic noise requirements of the traction motor are stringent; the current margin of the power device is reduced. Therefore, higher requirements are put forward for the modulation strategy, harmonic performance, current spikes, etc. of the traction system.

[0004] Currently, the synchronous modulation strategies include selective harmonic elimination pulse width modulation (SHEPWM), 60-degree intermediate modulation, and synchronous SVPWM. Among them, as an optimized synchronous modulation strategy, SHEPWM can eliminate specific harmonics and achieve accurate control of the fundamental voltage. However, the digital implementation of SHEPWM is relatively complex, and phase-by-phase switching is required during the switching between frequency divisions. When the frequency is switched, the motor speed changes greatly, resulting in a certain impact, which is prone to overcurrent faults, and the harmonics are relatively large in some intervals. The 60-degree intermediate modulation only controls the amplitude of the fundamental voltage, with a simple algorithm and easy implementation, but it cannot eliminate the low-order harmonics that have a greater impact on the motor, and the current spikes and total harmonics are relatively large. Synchronous SVPWM, as a quasi-optimal modulation strategy, has a simple algorithm, occupies less computing resources, and is easy to be digitally implemented. However, currently, when selecting the modulation strategy for each section of the full speed range, only the waveform symmetry is considered, and the overall electromagnetic noise and current spikes are not taken into account. For the modulation strategy with angle overlap before and after the switching between frequency divisions, the existing methods do not mention how to achieve smooth switching. For power devices, the narrower the pulse limit, the better; but for control, the smaller the narrow pulse, the better, and the two are contradictory. Due to the dead zone and narrow pulse limit, it is impossible to achieve a completely seamless transition between the 3-frequency division and the square wave. As the modulation degree gradually approaches The pulse width of the 3 - frequency - division part becomes narrower and narrower. According to the existing transition method between 3 - frequency - division and square wave, it is very easy to generate narrow pulses that are harmful to power devices, which will have a certain impact on the device life after long - term use. At present, the existing pulse generation method is not flexible enough. When there are more than 2 effective switching angles in a modulation period, pulses cannot be generated as required.

[0005] To solve the above - mentioned technical problems, a method for achieving low electromagnetic noise, small current harmonics and spikes, no impact and no harmful narrow - pulse control in the full - speed range of the train is particularly important. Summary of the Invention

[0006] The purpose of the embodiment of the present invention is to provide a method based on segmented synchronous SVPWM to achieve low electromagnetic noise, small current harmonics and spikes, no impact and no harmful narrow - pulse control.

[0007] The present invention provides a method based on segmented synchronous SVPWM, and the method includes:

[0008] The first processor determines the required modulation degree according to the motor line voltage and the DC bus voltage;

[0009] Obtain the stator frequency, the frequency - division number and the actual execution angle interval of the previous modulation period;

[0010] According to the required modulation degree, the stator frequency and the actual execution angle interval, determine whether to switch frequencies; and when switching frequencies, determine the frequency - division number of this period, and determine the sampling angle according to the frequency - division number of this period;

[0011] According to the frequency - division number, correct the required modulation degree to obtain the corrected modulation degree;

[0012] According to the frequency - division number and the stator frequency, calculate the first and second modulation periods of this period; according to the first and second modulation periods, the sampling angle and the corrected modulation degree, calculate the comparison value at the sampling angle;

[0013] According to the comparison value, determine the angles of the three - phase pulse switching angles of this period; according to the initial vector at the initial moment of this period, determine the initial levels of the three - phase pulses; send the first modulation period, the angles of the three - phase pulse switching angles and the initial levels to the second processor for pulse control. In a possible implementation manner, the determining the required modulation degree according to the motor line voltage and the DC bus voltage specifically includes:

[0014] Determine the required modulation degree according to the ratio of the motor line voltage to the DC bus voltage.

[0015] In a possible implementation manner, the determining whether to switch frequencies according to the required modulation degree, the stator frequency and the actual execution angle interval specifically includes:

[0016] During acceleration, if the required modulation degree is greater than a preset first threshold value, or the stator frequency is greater than a preset second threshold value, and the actual execution angle interval meets the preset conditions, the frequency division number is switched from high frequency to low frequency;

[0017] During deceleration, if the required modulation degree is not greater than the set first threshold value, or the stator frequency is not greater than the preset second threshold value, and the actual execution angle interval meets the preset conditions, the frequency division number is switched from low frequency to high frequency;

[0018] The preset conditions are specifically as follows: the actual execution angle intervals of the previous cycle and the actual execution angle interval after frequency switching do not overlap and have no interval; and, before and after frequency switching, the three-phase switching devices do not act or there is at least one zero vector and at most only one of the three-phase switching devices acts.

[0019] In a possible implementation manner, before the method, it further includes:

[0020] Determine multiple frequency division numbers, and the sampling angles of the sampling points corresponding to each frequency division number among the multiple frequency division numbers;

[0021] According to the sampling angles corresponding to each frequency division number, determine the actual execution angle interval of each sampling angle;

[0022] Judge whether the actual execution angle intervals corresponding to the sampling angles overlap when switching frequencies between adjacent frequency division numbers;

[0023] When the actual execution angle intervals overlap, re-divide the overlapping actual execution angle intervals, and replace the previous actual execution angle intervals with the new actual execution angle intervals; store the frequency division number, the sampling angles corresponding to the frequency division number, the actual execution angle intervals corresponding to the sampling angles, or the new actual execution angle intervals corresponding to the sampling angles.

[0024] In a possible implementation manner, the obtaining of the stator frequency and the frequency division number and the actual execution angle interval of the previous modulation cycle specifically includes:

[0025] According to the frequency division number of the previous modulation cycle, determine the sampling angle of the previous cycle;

[0026] According to the sampling angle of the previous cycle, calculate the actual execution angle interval of each sampling angle.

[0027] In a possible implementation manner, the calculating of the actual execution angle interval of each sampling angle according to the sampling angle of the previous cycle specifically includes:

[0028] Subtract the quotient of 360 degrees divided by twice the number of all sampling angles from each sampling angle, and use the result as the starting angle of the actual execution angle interval;

[0029] Add the quotient of 360 degrees divided by twice the number of all sampling angles to each sampling angle, and use the result as the ending angle of the actual execution angle interval.

[0030] In a possible implementation, the frequency division numbers include CSVS_15 frequency division, CSVS_12 frequency division, CSVS_9 frequency division, BSS_7 frequency division, AZCS_5 frequency division, and CSVS_3 frequency division;

[0031] The BSS_7 frequency division and CSVS_3 frequency division are used to re-divide the actual execution angle interval to obtain a new actual execution angle interval.

[0032] In a possible implementation, the specific process of correcting the required modulation degree according to the frequency division number to obtain the corrected modulation degree includes:

[0033] According to the maximum actual modulation degree corresponding to each frequency division number and the relationship between the actual modulation degree and the theoretical modulation degree, starting from the initial value, increase the actual modulation degree in accordance with a preset step size, determine the theoretical modulation degree after each increase, and store the actual modulation degree and the corresponding theoretical modulation degree after each increase in an array;

[0034] According to the required modulation degree and the frequency division number of this cycle, determine the actual modulation degree corresponding to the required modulation degree, determine the array corresponding to the actual modulation degree, and read the theoretical modulation degree in the array as the corrected modulation degree.

[0035] In a possible implementation, the specific process of calculating the first and second modulation periods of this cycle according to the frequency division number and the stator frequency includes:

[0036] When the actual execution angle interval is not re-divided, determine the first modulation period of this cycle according to the product of the carrier ratio corresponding to the frequency division number and the stator frequency;

[0037] When the actual execution angle interval is re-divided, determine the first modulation period of this cycle according to the product of the carrier ratio after re-dividing the actual execution angle interval and the stator frequency; determine the second modulation period of this cycle according to the product of the carrier ratio when the actual execution angle interval is not re-divided and the stator frequency.

[0038] Among them, for the frequency division without re - dividing the actual execution angle interval, the first period is used both for calculating the modulation period value and for calculating the comparison value; for the frequency division with re - dividing the actual execution angle interval, the first period is used for calculating the modulation period value, and the second period is used for calculating the comparison value. In a possible implementation manner, the comparison value includes two non - zero vector action times and one zero vector action time. The calculating the comparison value at the sampling angle according to the first and second modulation periods, the sampling angle, and the corrected modulation degree specifically includes:

[0039] Calculating two non - zero vector action times and one zero vector action time at the sampling angle according to the first and second modulation periods and the corrected modulation degree.

[0040] Thus, by applying the method based on segmented synchronous SVPWM provided by the present invention, in the full - speed range of the train, within the low - frequency division, segmented processing is performed, and low electromagnetic noise, small current harmonics and spikes, and shock - free and harmless narrow - pulse control can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic flowchart of the modulation strategy generation method provided by an embodiment of the present invention;

[0042] Figure 2 It is a schematic flowchart of the method based on segmented synchronous SVPWM provided by an embodiment of the present invention;

[0043] Figure 3 It is a schematic diagram of the full - speed - range segmented synchronous SVPWM pulse - width modulation strategy provided by an embodiment of the present invention;

[0044] Figure 4 It is a schematic diagram of the SVPWM space voltage vector distribution provided by an embodiment of the present invention;

[0045] Figure 5 It is a current waveform diagram of 15 - frequency - division cutting to 12 - frequency - division provided by an embodiment of the present invention;

[0046] Figure 6 It is a current waveform diagram of 12 - frequency - division cutting to 9 - frequency - division provided by an embodiment of the present invention;

[0047] Figure 7 It is a space voltage vector diagram of the first sector after re - dividing the 7 - frequency - division provided by an embodiment of the present invention;

[0048] Figure 8 It is a U - phase pulse sequence diagram before re - dividing the 7 - frequency - division provided by an embodiment of the present invention;

[0049] Figure 9 It is a U - phase pulse sequence diagram after re - dividing the 7 - frequency - division provided by an embodiment of the present invention;

[0050] Figure 10 The current waveform diagram of dividing 9 - frequency into 7 - frequency provided by the embodiment of the present invention;

[0051] Figure 11 The current waveform diagram of dividing 7 - frequency into 5 - frequency provided by the embodiment of the present invention;

[0052] Figure 12 The pulse sequence diagrams of U, V, and W phases before re - partitioning the square wave with 3 - frequency provided by the embodiment of the present invention;

[0053] Figure 13 The pulse sequence diagrams of U, V, and W phases after re - partitioning the square wave with 3 - frequency provided by the embodiment of the present invention;

[0054] Figure 14 The current waveform diagram of dividing 5 - frequency into 3 - frequency provided by the embodiment of the present invention;

[0055] Figure 15 The current waveform diagram of dividing 3 - frequency into square wave provided by the embodiment of the present invention;

[0056] Figure 16 The schematic diagram of carrier wave before and after frequency conversion provided by the embodiment of the present invention;

[0057] Figure 17 The schematic diagram of FPGA PWM pulse generation provided by the embodiment of the present invention. Detailed implementation manners

[0058] The following further elaborates on the present application in combination with the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the relevant invention rather than to limit the invention. Additionally, it should be noted that for the convenience of description, only parts related to the relevant invention are shown in the drawings.

[0059] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The following will detail the present application with reference to the accompanying drawings and embodiments.

[0060] For power devices, especially high - power devices, when the frequency division number is small, directly applying synchronous SVPWM will cause harmful narrow pulses in the full - speed range. Therefore, the segmented synchronous SVPWM method of the present application can perform frequency conversion on the frequency division number, thereby avoiding the appearance of harmful narrow pulses. Among them, frequency conversion refers to the switching of the frequency division number. The following will explain how to perform frequency conversion specifically. The frequency division number is the switching frequency, that is, the ratio of the pulse to the fundamental wave frequency, that is, the stator frequency.

[0061] In this application, for segmented SVPWM, it is necessary to first determine the frequency division number, sampling angle, and actual execution angle interval, so that when the frequency is switched later, after the frequency division number is determined, the sampling angle and actual execution angle interval corresponding to the frequency division number can be directly read. Then, the comparison value at the sampling angle is calculated through the actual execution angle interval, the angle of the three-phase pulse switching angle is determined through the comparison value, the initial level of the three-phase pulse is determined through the initial moment vector, and the pulse is controlled according to the angle and the initial level to avoid the occurrence of harmful narrow pulses.

[0062] Before explaining the method of segmented synchronous SVPWM of this application, first explain how to determine the actual execution angle interval corresponding to the frequency division number. As Figure 1 shown, it includes the following steps:

[0063] Step 110, determine multiple frequency division numbers, and the sampling angle corresponding to each frequency division number among the multiple frequency division numbers;

[0064] Specifically, in the train traction system, the traction inverter is the core of the traction system. The traction inverter is generally a two-level three-phase inverter. For a two-level three-phase inverter, there are 6 switching devices. According to the different switching states of the devices, 2 3 ^6 = 64 different space voltage vectors can be obtained, including 2 zero voltage vectors and 6 effective voltage vectors. The 6 effective voltage vectors are represented as (1, 2... 6), and the 2 zero voltage vectors are represented as (0, 7). The effective voltage vectors divide the entire complex plane into 6 sectors, each sector being 60°. Taking the first sector as an example, 0 and 7 represent zero voltage vectors, and 1 and 2 represent effective voltage vectors, as Figure 3 shown.

[0065] According to the number of sampling points in each sector, the sampling angle of the sampling points, and the action order of the sampling point vectors, synchronous SVPWM modulation can be further divided into the conventional space vector strategy (CSVS), the boundary sampling strategy (BSS), the asymmetric zero vector conversion strategy (AZCS), and the basic bus clamping strategy (BBCS).

[0066] Among them, taking the first sector as an example, the action sequence of the sampling point vectors is described. The first sector has four vectors: 0, 1, 2, and 7, where 0 and 7 are zero vectors. The SVPWM modulation method acts in a certain order, such as 0127, 7210. The action sequence is determined according to the specific modulation strategy method selected. For example, if CSVS is selected, the switching sequence can only be 0127 or 7120.

[0067] Although the BBCS_7 frequency division can directly achieve smooth switching without angular overlap with the 9 and 5 frequency divisions, the overall harmonics are relatively large and the current spikes are relatively large, which is not conducive to the motor temperature rise and the life of the power devices. Therefore, the BSS_7 with good harmonic performance and small current spikes is adopted in this application.

[0068] Therefore, in order to reduce the electromagnetic noise, current harmonics and current spikes in the full-speed range of the train, the segmented synchronous SVPWM in this application selects CSVS_15, CSVS_12, CSVS_9, BSS_7, AZCS_5, CSVS_3, hereinafter referred to as 15 frequency division, 12 frequency division, 9 frequency division, 7 frequency division, 5 frequency division, 3 frequency division.

[0069] The modulation strategy in this application and the sampling angles corresponding to the sampling points in the first sector are as Figure 4 shown in Table 1:

[0070] Frequency division number Modulation strategy First sector sampling angle 15 CSVS 6°，18°，30°，42°，54° 12 CSVS 7.5°，22.5°，37.5°，42.5° 9 CSVS 10°，30°，50° 7 BSS 0°，20°，40° 5 AZCS 15°，45° 3 CSVS 30° Square wave / /

[0071] Table 1

[0072] For the convenience of subsequent frequency switching, each frequency division number corresponds to a frequency division counter value. Thus, when switching frequencies, the frequency division counter is directly incremented by 1 to achieve frequency switching from low frequency to high frequency, or the frequency division counter is decremented by 1 to achieve frequency switching from high frequency to low frequency, as shown in Table 2:

[0073] Frequency division counter Frequency division number Modulation strategy First sector sampling angle 1 15 CSVS 6°，18°，30°，42°，54° 2 12 CSVS 7.5°，22.5°，37.5°，42.5° 3 9 CSVS 10°，30°，50° 4 7 BSS 0°，20°，40° 5 5 AZCS 15°，45° 6 3 CSVS 30° 7 Square wave / /

[0074] Table 2

[0075] Step 120, determine the actual execution angle interval of each sampling angle according to the sampling angles corresponding to each frequency division number;

[0076] Specifically, fixed sampling angles X1, X2... X i are set in each sector. Each sampling angle corresponds to an actual execution angle interval, and the actual action angle interval corresponding to each sampling angle is shown in the following formula:

[0077]

[0078] Among them, X i is the sampling angle, and i is the number of all sampling angles in the 6 sectors corresponding to the frequency division number.

[0079] Step 130: When determining the frequency switching between adjacent frequency division numbers, check whether the actual execution angle intervals corresponding to the sampling angles overlap;

[0080] Step 140: When the actual execution angle intervals overlap, re-divide the overlapping actual execution angle intervals, and replace the previous actual execution angle intervals with the new actual execution angle intervals;

[0081] Specifically, before and after the switching between each frequency division, the fundamental voltage and current should be ensured to be continuous. For smooth switching, the following frequency switching conditions need to be met: ① There is no overlap and no gap between the actual execution angle intervals of the two sampling points before and after the switching; ② Before and after the switching, the three-phase switching devices do not operate or at least one zero vector exists and at most only one of the three phases operates. Among them, the non-operation of the three-phase switching devices before and after the switching means that the states of the switching devices are the same before and after the frequency switching, and no switching action is performed, that is, the vectors are the same before and after the frequency switching. Only one action of the three phases means that after the frequency switching, compared with before the frequency switching, at most one of the three-phase switching devices operates, and the other two states remain unchanged.

[0082] The following explains whether each frequency division meets the switching conditions during frequency switching:

[0083] For the 15-frequency division, 12-frequency division, and 9-frequency division, CSVS is adopted. The number of sampling points in each sector is 5, 4, and 3 respectively. The sampling points are evenly distributed in each sector and are symmetric about the sector midpoint HY. The voltage vectors at the head and tail of each sampling point are zero vectors, and the actual execution angle intervals of all sampling points in each sector are (Y - 1)*60° to Y*60°. Therefore, during frequency switching, the 15-frequency division, 12-frequency division, and 9-frequency division do not require re-division of the actual execution angle intervals. Among them, Y is the sector number, 1, 2... 6. HY is the sector midpoint angle, HY = Y*30°.

[0084] The entire complex plane is divided into 30, 24, and 18 actual execution angle intervals respectively, hereinafter referred to as small intervals, that is, the carrier ratio N = 30, 24, 18. The carrier ratio refers to the ratio of the carrier frequency to the fundamental frequency (stator frequency). A carrier ratio of 30 means there are 30 carriers in one fundamental wave period.

[0085] (1) Frequency switching between the 15-frequency division and the 12-frequency division

[0086] Due to the inherent characteristics of even frequency division, although the positive and negative half-waves of the 12-frequency division are not completely symmetric, the number of pulses within one fundamental wave is relatively large, which has less impact on harmonics. Moreover, since both ends of each sampling point in the 12-frequency division are 0 voltage vectors, the noise is low. Therefore, in this application, the 12-frequency division is adopted between the 15-frequency division and the 9-frequency division.

[0087] The sampling angles of the first sector for the 15 - frequency division are 6°, 18°, 30°, 42°, 54°. The actual execution angle intervals for each sampling angle are 0° - 12°, 12° - 24°, 24° - 36°, 36° - 48°, 48° - 60° respectively. According to the actual execution angle intervals, the entire complex plane can be divided into 30 small intervals numbered 1, 2... 30, that is, the carrier ratio N = 30.

[0088] The sampling angles of the sampling points in the first sector for the 12 - frequency division are 7.5°, 22.5°, 37.5°, 52.5°. According to the actual execution angle intervals, the entire complex plane can be divided into 24 small intervals numbered 1, 2... 24, that is, the carrier ratio N = 24.

[0089] According to the above switching conditions, when switching from 15 - frequency division to 12 - frequency division, the selectable small intervals for the 15 - frequency division before switching are 10, 20, 30, and the selectable small intervals for the 12 - frequency division after switching are 9, 17, 1. When switching from 12 - frequency division to 15 - frequency division, the selectable small intervals for the 12 - frequency division before switching are 8, 16, 24, and the selectable small intervals for the 15 - frequency division after switching are 11, 21, 1.

[0090] The switching condition is met when the boundary of the actual execution angle interval is Z * 120°, where Z is 1, 2, 3. There is no overlap in the angles before and after switching, and no action is taken on the three - phase switching devices. The actual switching waveform is as Figure 5 shown.

[0091] Taking the 10th small interval of the 15 - frequency division as an example, the actual execution angle interval is 108° - 120°, and the vector action sequence is 7320. After switching to the 9th small interval of the 12 - frequency division, the actual execution angle interval is 120° - 135°, and the vector action sequence is 0347. The actual execution angles before and after switching are continuous, the tail and head vectors are both zero vectors, and no action is taken on the three - phase.

[0092] (2) Switching between 12 - frequency division and 9 - frequency division

[0093] Specifically, the sampling angles of the first sector for the 9 - frequency division are 10°, 30°, 50°. According to the actual execution angle intervals, the entire complex plane can be divided into 18 small intervals numbered 1, 2... 18, that is, the carrier ratio N = 18.

[0094] Then, according to the above switching conditions, when switching from 12 - frequency division to 9 - frequency division, the selectable small intervals for the 12 - frequency division before switching are 8, 16, 24, and the selectable small intervals for the 9 - frequency division after switching are 7, 13, 1. When switching from 9 - frequency division to 12 - frequency division, the selectable small intervals for the 9 - frequency division before switching are 6, 12, 18, and the selectable small intervals for the 12 - frequency division after switching are 9, 17, 1.

[0095] That is, when the actual execution angle interval boundary is Z * 120°, the switching condition is met, and there is no overlap in the angles before and after switching, and the three-phase switching devices do not operate, where Z is 1, 2, or 3. The actual switching waveform is as Figure 6 shown.

[0096] Taking the 8th small interval of the 12 - frequency division as an example, the actual execution angle interval is 105° to 120°, and the vector action sequence is 7320. After switching to the 9 - frequency division, it is the 7th small interval, and the actual execution angle interval is 120° to 140°, and the vector action sequence is 0347. The actual execution angles before and after switching are continuous, and the tail and head vectors are both zero vectors, and the three - phase has no action.

[0097] (3) Switching between 9 - frequency division and 7 - frequency division

[0098] Specifically, the number of sampling points in each sector of the 7 - frequency division is 3. The sampling angles of the first sector are 0°, 20°, and 40°. The actual execution angle intervals corresponding to each sampling angle are 350° to 10°, 10° to 30°, and 30° to 50° in turn, as Figure 7 shown. Due to the existence of the sampling points (Y - 1) * 60° at the sector boundary, the actual execution angle interval spans two sectors, which is (Y - 1) * 60° - 10° to (Y - 1) * 60° + 10°. Switching with the 9 - frequency division and 5 - frequency division cannot meet the above - mentioned switching conditions, and there are angle overlaps or intervals. As Figure 8 shown.

[0099] Since the sampling angles of the boundary sampling points are 0°, 60°, 120°, 180°, 240°, and 300°, the two ends of the voltage vector action sequence are the same zero vectors, and there is only one effective voltage vector in the middle. The actual execution angle interval is symmetric about the sampling point. Therefore, in this application example, the 7 - frequency division is re - partitioned, and the small intervals of the boundary sampling points are evenly divided into 2 small intervals and merged into the adjacent non - boundary sampling point small intervals. As Figure 9 shown, after re - partitioning, the sampling points of the first sector are [0°2, 20°], [40°, 60°1], where 0°2 represents the sampling point with the actual execution angle interval of 0° to 10°, 20° is the sampling angle of 20°, and the actual execution angle interval is 10° to 30°, and 60°1 represents the sampling point with the actual execution angle interval of 50° to 60°. Then, for the sampling point [0°2, 20°], the actual execution angle interval is 0° to 30°, and for the sampling point [40°, 60°1], the actual execution angle interval is 30° to 60°.

[0100] The 18 small intervals are re - divided into 12 small intervals numbered 1, 2... 12, that is, the carrier ratio N = 12.

[0101] According to the above switching conditions, when switching from the 9 - frequency division to the 7 - frequency division, the selectable small intervals before switching in the 9 - frequency division are 3, 6, 9, 12, 15, 18, and the selectable small intervals after switching in the 7 - frequency division are 3, 5, 7, 9, 11, 1. When switching from the 7 - frequency division to the 9 - frequency division, the selectable small intervals before switching in the 7 - frequency division are 2, 4, 6, 8, 10, 12, and the selectable small intervals after switching in the 9 - frequency division are 4, 7, 10, 13, 16, 1.

[0102] That is, when the actual execution angle interval boundary is Z * 60°, the switching condition is met. There is no overlap in the angles before and after switching, only one of the three - phase switching devices acts, and the trailing vector of the 9 - frequency division before switching is the zero vector, where Z is 1, 2... 6. The actual switching waveform is as Figure 10 shown.

[0103] Taking the 3rd small interval of the 9 - frequency division as an example, the actual execution angle interval is 40° - 60°, and the vector action sequence is 0127. When switching to the 3rd small interval of the 7 - frequency division, the actual execution angle interval is 60° - 90°, and the vector action sequence is 27723. The actual execution angles before and after switching are continuous, the trailing vector of the 9 - frequency division is the zero vector, and only the W - phase acts.

[0104] (4) Switching between the 7 - frequency division and the 5 - frequency division

[0105] Specifically, the number of sampling points in each sector of the 5 - frequency division is 2. The sampling points are evenly distributed in each sector and are symmetric about the sector mid - point. Each sampling point has two effective voltage vectors, but only one zero - voltage vector, which is located at the head or the tail. The sampling angles in the first sector are 15°, 45°. The actual execution angle intervals of the sampling points in each sector are (Y - 1) * 60° - Y * 60°. The actual execution angle intervals corresponding to each sampling angle are 0° - 30°, 30° - 60° in turn. Then the entire complex plane can be divided into 12 small intervals numbered 1, 2... 12, that is, the carrier ratio N = 12.

[0106] Then, when the actual execution angle interval boundary is Z * 60°, the 7 - and 5 - frequency divisions meet the switching conditions. When switching from the 7 - frequency division to the 5 - frequency division, the selectable small intervals before switching in the 7 - frequency division are 2, 4, 6, 8, 10, 12, and the selectable small intervals after switching in the 5 - frequency division are 3, 5, 7, 9, 11, 1. When switching from the 7 - frequency division to the 9 - frequency division, the selectable small intervals before switching in the 7 - frequency division are 2, 4, 6, 8, 10, 12, and the selectable small intervals after switching in the 9 - frequency division are 3, 5, 7, 9, 11, 1.

[0107] That is, when the actual execution angle interval boundary is Z * 60°, the switching condition is met. There is no overlap in the angles before and after switching between the 9 - and 7 - frequency divisions, only one of the three - phase switching devices acts, and the leading vector of the 5 - frequency division after switching is the zero vector, where Z is 1, 2... 6. The actual switching waveform is as Figure 11 shown.

[0108] Taking the second small interval of the 7 - frequency division as an example, the actual execution angle interval is 30° to 60°, and the vector action sequence is 12772. When switching to the 5 - frequency division for the third small interval, the actual execution angle interval is 60° to 90°, and the vector action sequence is 723. The actual execution angles before and after switching are continuous. The first vector of the 5 - frequency division is the zero vector, and only the W - phase acts.

[0109] (5) Switching between 5 - frequency division and 3 - frequency division

[0110] Specifically, the number of sampling points in each sector of the 3 - frequency division is 1, the sampling angle of the sampling point is Y * 30, the sampling angle of the first sector is 30°, the actual execution angle interval is (Y - 1) * 60° to Y * 60°, and the actual execution angle interval of the sampling point in the first sector is 0° to 60°. Although it meets the condition of smooth switching with the 5 - frequency division, when transitioning to the square wave, due to the dead zone and minimum pulse width limitations, harmful narrow pulses are likely to be generated, which has a certain impact on the safe use of switching devices, as Figure 12 shown.

[0111] Therefore, this application needs to re - divide the 3 - frequency division. Since the action times of the two effective voltage vectors of the sampling point are equal, the sampling angle of the sampling point in the first sector of the 3 - frequency division is 30°, and the action times of the two vectors are the same, both being Therefore, the sampling point interval can be split into two small intervals, and the entire complex plane is split into 12 small intervals. After re - dividing, the sampling angles of the sampling points in the first sector are 30°1 and 30°2, where 30°1 represents the sampling point with the actual execution angle interval of 0° to 30°, and 30°2 represents the sampling point with the actual execution angle interval of 30° to 60°, as Figure 13 shown. The complex plane is re - divided into 12 small intervals numbered 1, 2... 12, that is, the carrier ratio N = 12.

[0112] Then, according to the above - mentioned switching conditions, when switching from 5 - frequency division to 3 - frequency division, the selectable small intervals of the 5 - frequency division before switching are 2, 4, 6, 8, 10, 12, and the selectable small intervals of the 3 - frequency division after switching are 3, 5, 7, 9, 11, 1. When switching from 3 - frequency division to 5 - frequency division, the selectable small intervals of the 3 - frequency division before switching are 2, 4, 6, 8, 10, 12, and the selectable small intervals of the 5 - frequency division after switching are 3, 5, 7, 9, 11, 1. The actual switching waveform is as Figure 14 shown.

[0113] Taking the second small interval of the 5 - frequency division as an example, the actual execution angle interval is 30° to 60°, and the vector action sequence is 127. When switching to the 3 - frequency division for the third small interval, the actual execution angle interval is 60° to 90°, and the vector action sequence is 72. The actual execution angles before and after switching are continuous. The first and last vectors are both zero vectors, and no phase acts.

[0114] To achieve smooth switching with no narrow pulses for the three - phase division, the initial stage of the square wave also uses 12 small intervals, that is, the carrier ratio N = 12. In the later stage, in order to reduce the execution frequency of the modulation program, it is reduced to 6 small intervals at an appropriate speed point, that is, the carrier ratio N = 6.

[0115] When the modulation degree of the three - phase division is greater than the set threshold, it directly switches to the square wave in the odd - numbered small intervals. When the modulation degree is less than the set threshold, it can return to the three - phase division in the odd - numbered small intervals. The actual switching waveform is as Figure 15 shown.

[0116] The final obtained frequency division number, the sampling angle of the sampling point, and the actual execution angle interval are shown in Table 3:

[0117]

[0118] Table 3

[0119] In this application, the concept of re - dividing the actual execution angle interval is introduced, and the seven - phase division and the three - phase division are re - divided to make the seven - phase division satisfy smooth switching with the nine - phase division and the five - phase division, and the three - phase division and the square wave achieve harmless narrow - pulse smooth transition. Other frequency divisions using different modulation strategies can also be flexibly divided in practical applications to achieve smooth switching and reduce the carrier ratio.

[0120] Step 150, store the frequency division number, the sampling angle corresponding to the frequency division number, the actual execution angle interval corresponding to the sampling angle, or the new actual execution angle interval corresponding to the sampling angle.

[0121] Specifically, store the frequency division number, the sampling angle corresponding to the frequency division number, the actual execution angle interval corresponding to the sampling angle, or the new actual execution angle interval corresponding to the sampling angle in the storage module of the first processor, so as to be directly called during subsequent pulse modulation, thereby saving processing time.

[0122] Figure 2 This is a schematic flowchart of the method based on segmented synchronous SVPWM provided in the first embodiment of the present invention. The execution subject of this method is the first processor, and the first processor can be a Digital Signal Processing (DSP). As Figure 2 shown, this method includes the following steps:

[0123] Step 210, the first processor determines the required modulation degree according to the motor line voltage and the DC bus voltage;

[0124] Among them, the motor line voltage refers to the voltage between two lines in a polyphase power supply system. Taking three-phase as an example, it is the voltage between the outgoing lines of phases A, B, and C, also known as the line voltage. The DC bus voltage refers to the voltage obtained by converting AC to DC and is installed in the form of a copper busbar in the frequency converter. Specifically, the required modulation ratio can be calculated through the ratio of the motor line voltage to the DC bus voltage. Here, the required modulation ratio is the actual modulation ratio that is currently desired to achieve. As shown in the following formula:

[0125]

[0126] Among them, m is the required modulation ratio, U m is the motor line voltage, U d is the DC bus voltage,

[0127] Step 220: Obtain the stator frequency, the division number of the previous modulation period, and the actual execution angle interval;

[0128] Specifically, according to the division number of the previous modulation period, determine the sampling angle of the previous period; according to the sampling angle of the previous period, calculate the actual execution angle interval of each sampling angle.

[0129] During the execution process, the division number and the actual execution angle interval of each period will be stored, and the division number and the actual execution angle interval of the previous period stored can be directly called to facilitate subsequent judgment on whether frequency switching is required in this period.

[0130] Step 230: Determine whether to switch frequencies according to the required modulation ratio, the stator frequency, and the actual execution angle interval; and when switching frequencies, determine the division number of this period and determine the sampling angle according to the division number of this period;

[0131] Specifically, determining whether to switch frequencies includes: when accelerating, if the required modulation ratio is greater than the preset first threshold, or the stator frequency is greater than the preset second threshold, and the actual execution angle interval meets the preset conditions, the division number is switched from high frequency to low frequency; when decelerating, if the required modulation ratio is not greater than the set first threshold, or the stator frequency is not greater than the preset second threshold, and the actual execution angle interval meets the preset conditions, the division number is switched from low frequency to high frequency.

[0132] Among them, the preset conditions are specifically: there is no overlap and no gap between the actual execution angle interval of the previous period and the actual execution angle interval after frequency switching; and, before and after frequency switching, the three-phase switching devices do not act or there is at least one zero vector and at most only one of the three-phase switching devices acts.

[0133] Among them, the first threshold and the second threshold are empirical values set according to actual experience.

[0134] When accelerating, if frequency division is determined, the frequency division number can be switched from high frequency to low frequency. As for how many frequency divisions to switch to, it can be determined by querying. Generally, it is switched to the adjacent frequency division number. For example, from 15 - frequency division to 12 - frequency division. When decelerating, the frequency division number can be switched from low frequency to high frequency, such as from 12 - frequency division to 15 - frequency division.

[0135] After determining the frequency switching, determine the value of the frequency - division counter. By querying, the actual execution angle range corresponding to the frequency - division number can be obtained.

[0136] Step 240, according to the frequency - division number, correct the required modulation degree to obtain the corrected modulation degree;

[0137] Specifically, step 240 includes: according to the maximum actual modulation degree corresponding to each frequency - division number and the relationship between the actual modulation degree and the theoretical modulation degree, starting from the initial value, the actual modulation degree is incremented by a preset step size. Determine the theoretical modulation degree after each increment, and store the actual modulation degree and the corresponding theoretical modulation degree after each increment in an array; according to the required modulation degree and the frequency - division number of this cycle, determine the actual modulation degree corresponding to the required modulation degree, determine the array corresponding to the actual modulation degree, and read the theoretical modulation degree in the array as the corrected modulation degree. Among them, the corrected modulation degree is the theoretical modulation degree; the actual modulation degree is the actual modulation degree during pulse modulation. The above - mentioned corresponding relationship can be obtained through multiple experiments. For example, assign a value to the theoretical modulation degree, then calculate the corresponding actual modulation degree, and then calculate the relationship between the theoretical modulation degree and the actual modulation degree. Thus, store the corresponding relationship between the actual modulation degree and the theoretical modulation. In the application of this application, under the current frequency - division number, the actual modulation degree corresponding to the required modulation degree can be determined, and then the theoretical modulation degree corresponding to this actual modulation degree is used to correct the required modulation degree.

[0138] For example, according to a step size of 0.001, the actual modulation degree of 5 - frequency division is 0.737. Starting from the initial value of 0 for 0 - 0.737 and incrementing by the step size, after each increment, an actual modulation degree corresponds to a theoretical modulation degree. Store the theoretical modulation degree corresponding to this actual modulation degree in an array. An array of size 738 is required, and each element in the array corresponds to a modulation degree.

[0139] In the application, if it is 5 - frequency division and the current required modulation degree m = 0.612, then directly read the theoretical modulation degree in the array a5

[612] corresponding to the actual modulation degree of 0.612, and correct the current modulation degree with the theoretical modulation degree in the array.

[0140] Step 250, according to the frequency - division number and the stator frequency, calculate the first modulation period of this cycle; according to the first modulation period, the sampling angle, and the corrected modulation degree, calculate the comparison value at the sampling angle.

[0141] Specifically, the first modulation period of this cycle is determined according to the product of the carrier ratio corresponding to the frequency division number and the stator frequency. The first modulation period can be specifically calculated according to the following formula:

[0142]

[0143] where T pwm is the first modulation period, N is the carrier ratio, and F s is the stator frequency.

[0144] According to the SVPWM volt-second balance principle, in an interval with two sampling angles θ1 and θ2, the comparison value at the sampling angle θ1 includes the zero vector action time T 01 and the action times T 11 , T 21 of two basic voltage vectors. The comparison value at the sampling angle θ2 includes the zero vector action time T 02 and the action times T 12 , T 22 of two basic voltage vectors. The comparison value can be expressed by the following formula:

[0145]

[0146] where m′ is the corrected modulation degree. It should be noted that for the 7-frequency division and 3-frequency division, the actual execution angle intervals are re-divided. After re-dividing the actual execution angle intervals, the carrier ratio is 12 for both. However, when calculating the comparison value, the carrier ratios before re-dividing the actual execution angle intervals are used, which are 18 and 6 respectively.

[0147] In an example, taking the first actual execution angle interval of the 7-frequency division in the first sector as an example, the comparison value of the 7-frequency division at the sampling angle [0°2, 20°] is:

[0148]

[0149]

[0150] where the comparison value at 0°2 includes the zero vector action time T 01 and the action times T 11 , T 21 of two basic voltage vectors. The comparison value at 20° includes the zero vector action time T 02 and the action times T 12 , T 22 The first modulation period refers to the period after re-dividing the actual execution angle interval as The period before re-dividing the actual execution angle interval is used when calculating the comparison value, that is, the second modulation period is

[0151] In another example, taking the first actual execution angle interval of the first sector with a 3 - frequency division as an example, the comparison value at the sampling angle 30°1 for the 3 - frequency division is:

[0152]

[0153] Among them, since the 3 - frequency division re - divides the actual execution angle interval, the first modulation period refers to the period after re - dividing the actual execution angle interval. The second modulation period used to calculate the comparison value is

[0154] In yet another example, the vector action times at 15° and 45° for the 5 - frequency division are:

[0155]

[0156] Among them, T pwm is the first modulation period,

[0157] Step 260, according to the comparison value, determine the three - phase pulse switching angles and the initial levels of the three - phase pulse switching angles in this period.

[0158] Specifically, calculate the three - phase pulse switching angles α u1 、α u2 、α v1 、α v2 、α w1 、α w2 as follows:

[0159] α = f(T 1i , T 2i , T 0i )

[0160] Among them, α represents the three - phase pulse switching angle, including α u1 、α u2 、α v1 、α v2 、α w1 、α w2 , α u1 、α u2 represents the U - phase switching angle, α v1 、α v2 represents the V - phase switching angle, α w1 、α w2 represents the W - phase switching angle, T 1i , T 2i represents the action times of two basic voltage vectors,, T 0i represents the zero - vector action time.

[0161] In one example, taking the first actual execution angle interval of the first sector with a 7 - frequency division as an example, the three - phase pulse switching angles of the 7 - frequency division sampling angle [0°2, 20°] are as follows:

[0162]

[0163] In this modulation period, for the 7 - frequency division, there are two, one, and zero effective switching angles for phases U, V, and W respectively. Refer to Table 3. The initial vector is 1, that is, the initial levels are 1, 0, and 0 respectively.

[0164] In another example, taking the first actual execution angle interval of the first sector with a 3 - frequency division as an example, the switching angle of the 3 - frequency division sampling point 30°1 is as follows:

[0165]

[0166] In this modulation period, for the 3 - frequency division, only phase U has one effective switching angle. Refer to Table 3. The initial vector is 0, that is, the initial levels are 0, 0, and 0 respectively. After the 3 - frequency division switches to a square wave, all switching angles are assigned as T pwm , and only the initial levels are used for pulse generation.

[0167] Within one modulation period, each phase pulse of the 7 - frequency division has at most two effective switching angles, and other frequency divisions have at most one effective switching angle. 1 represents that the initial level of this modulation period is a high level, and 0 represents that the initial level is a low level.

[0168] When there is only one effective switching angle in this modulation period, the second ineffective switching angle α2 = T pwm . When there is no effective switching angle in this period, α1 = α2 = T pwm . Among them, the effective switching angle means that the switching angle value 0 < α < T pwm .

[0169] After the 3 - frequency division switches to a square wave, all switching angles are assigned as T pwm , and only the initial levels are used for pulse generation.

[0170] Step 270, send the three - phase pulse switching angles and the initial levels to the second processor for the second processor to perform pulse control.

[0171] Specifically, the second processor performs pulse control according to the three - phase pulse switching angles and the initial levels. Taking the second processor as a Field Programmable Gate Array (FPGA) as an example for illustration, as Figure 16As shown in the figure, the FPGA determines the level at the initial moment of the modulation period according to the received initial level. When encountering the effective switching angle 1, the level is flipped. When encountering the effective switching angle 2, the level is flipped again. If there are still effective switching angles, the level is flipped again. When there is no effective switching angle, the level of this modulation period remains unchanged according to the initial level, and the square wave only generates pulses using the initial level.

[0172] As Figure 17 shown, the initial level of Pulse 1 in Modulation Period 1 is 0, and there are two effective switching angles. When the initial level 0 encounters the first effective switching angle, the level is flipped to 1. When encountering the second effective switching angle, the level is flipped again to 0. The initial level of Pulse 1 in Modulation Period 2 is 0, and there is no effective switching angle, so the level remains at the initial level 0 during Modulation Period 2. The initial level of Pulse 2 in Modulation Period 1 is 1, and there are two effective switching angles. When the initial level 1 encounters the first effective switching angle, the level is flipped to 0. When encountering the second effective switching angle, the level is flipped again to 1. The initial level of Pulse 2 in Modulation Period 2 is 0. After entering Modulation Period 2 from Modulation Period 1, the level is flipped to 0, and there is no effective switching angle, remaining until the end of Modulation Period 2.

[0173] Therefore, the pulse generation adopts the method of combining the initial level with the switching angle. When the area is re-divided, there may be multiple effective switching angles in a single small time execution angle interval. According to the method of flipping the level according to the initial level and the effective switching angle encountered, the required synchronous pulses can be flexibly generated.

[0174] Therefore, by applying the method based on segmented synchronous SVPWM provided by the present invention, in the full-speed range of the train and within the low frequency division, segmented processing is performed, and low electromagnetic noise, small current harmonics and spikes, and shock-free and harmless narrow pulse control can be achieved.

[0175] Professionals should also be able to further realize that the units and algorithm steps of each example described in combination with the embodiments disclosed in this article can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professionals can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0176] The steps of the methods or algorithms described in connection with the embodiments disclosed herein may be implemented by hardware, software modules executed by a processor, or a combination of both. The software modules may be placed in a random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0177] The above specific implementation manners further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are only specific implementation manners of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method based on segmented synchronous SVPWM, characterized in that The method includes: The first processor determines a required modulation index based on the motor line voltage and the DC bus voltage; Obtain the stator frequency, the division ratio of the previous modulation period, and the actual execution angle range; Based on the required modulation index, the stator frequency, and the actual execution angle range, determine whether to perform frequency switching; and when performing frequency switching, determine the division ratio of this period, and determine the sampling angle according to the division ratio of this period; Modify the required modulation index according to the division ratio to obtain a modified modulation index; Calculate the first and second modulation periods of this period according to the division ratio and the stator frequency; calculate the comparison value at the sampling angle according to the first and second modulation periods, the sampling angle, and the modified modulation index; Determine the angles of the three-phase pulse switching angles of this period according to the comparison value; determine the initial levels of the three-phase pulses according to the initial vector at the initial moment of this period; Send the first modulation period, the angles of the three-phase pulse switching angles, and the initial levels to the second processor for pulse control; Among them, the determination of whether to perform frequency switching according to the required modulation index, the stator frequency, and the actual execution angle range specifically includes: When accelerating, if the required modulation index is greater than a preset first threshold, or the stator frequency is greater than a preset second threshold, and the actual execution angle range meets the preset conditions, the division ratio is switched from high frequency to low frequency; When decelerating, if the required modulation index is not greater than the set first threshold, or the stator frequency is not greater than the preset second threshold, and the actual execution angle range meets the preset conditions, the division ratio is switched from low frequency to high frequency; The preset conditions are specifically: there is no overlap and no gap between the actual execution angle range of the previous period and the actual execution angle range after frequency switching; and, before and after frequency switching, the three-phase switching devices do not operate or there is at least one zero vector and at most only one of the three-phase switching devices operates; The modification of the required modulation index according to the division ratio to obtain a modified modulation index specifically includes: According to the maximum actual modulation index corresponding to each division ratio and the relationship between the actual modulation index and the theoretical modulation index, increase the actual modulation index from the initial value in accordance with a preset step size, determine the theoretical modulation index after each increase, and store the actual modulation index and the corresponding theoretical modulation index after each increase in an array; Determine the actual modulation index corresponding to the required modulation index according to the required modulation index and the division ratio of this period, determine the array corresponding to the actual modulation index, and read the theoretical modulation index in the array as the modified modulation index; The calculation of the first and second modulation periods of this period according to the division ratio and the stator frequency specifically includes: When the actual execution angle range is not re-divided, determine the first modulation period of this period according to the product of the carrier ratio corresponding to the division ratio and the stator frequency; When the actual execution angle range is re-divided, determine the first modulation period of this period according to the product of the carrier ratio after re-dividing the actual execution angle range and the stator frequency; determine the second modulation period of this period according to the product of the carrier ratio when the actual execution angle range is not re-divided and the stator frequency; Among them, for the frequency division without re - dividing the actual execution angle interval, the first period is used for both the modulation period value calculation and the comparison value calculation; for the frequency division with re - dividing the actual execution angle interval, the first period is used for the modulation period value calculation, and the second period is used for the comparison value calculation; The comparison value includes two non - zero vector action times and one zero vector action time. The specific calculation of the comparison value at the sampling angle according to the first and second modulation periods, the sampling angle, and the corrected modulation degree includes: Calculating two non - zero vector action times and one zero vector action time at the sampling angle according to the first and second modulation periods and the corrected modulation degree.

2. The method according to claim 1, wherein The specific determination of the required modulation degree according to the motor line voltage and the DC bus voltage includes: Determining the required modulation degree according to the ratio of the motor line voltage to the DC bus voltage.

3. The method according to claim 1, characterized in that, Before the method, it also includes: Determining multiple frequency division numbers and the sampling angles of the sampling points corresponding to each frequency division number among the multiple frequency division numbers; Determining the actual execution angle interval of each sampling angle according to the sampling angle corresponding to each frequency division number; Judging whether the actual execution angle intervals corresponding to the sampling angles overlap when switching frequencies between adjacent frequency division numbers; When the actual execution angle intervals overlap, re - dividing the overlapping actual execution angle intervals and replacing the previous actual execution angle intervals with the new actual execution angle intervals; Storing the frequency division number, the sampling angle corresponding to the frequency division number, the actual execution angle interval corresponding to the sampling angle, or the new actual execution angle interval corresponding to the sampling angle.

4. The method according to claim 3, wherein The specific acquisition of the stator frequency, the frequency division number, and the actual execution angle interval of the previous modulation period includes: Determining the sampling angle of the previous period according to the frequency division number of the previous modulation period; Calculating the actual execution angle interval of each sampling angle according to the sampling angle of the previous period.

5. The method according to claim 4, characterized in that, The specific calculation of the actual execution angle interval of each sampling angle according to the sampling angle of the previous period includes: Subtracting the quotient of 360 degrees divided by twice the number of all sampling angles from each sampling angle as the starting angle of the actual execution angle interval; Adding the quotient of 360 degrees divided by twice the number of all sampling angles to each sampling angle as the ending angle of the actual execution angle interval.

6. The method according to claim 1, characterized in that, The frequency division numbers include CSVS_15 frequency division, CSVS_12 frequency division, CSVS_9 frequency division, BSS_7 frequency division, AZCS_5 frequency division, and CSVS_3 frequency division; The BSS_7 frequency division and CSVS_3 frequency division re - divide the actual execution angle interval to obtain a new actual execution angle interval.

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