阅读说明：本技术 一种逆变控制方法 (Inversion control method ) 是由 张长安 盛晨媛 于 2019-11-27 设计创作，主要内容包括：本公开提供了一种逆变控制方法,应用于三相逆变器,该方法包括：将三相逆变器各开关元件在逆变控制中的不同通断状态各编译为数字代码,每个数字代码依次包括对应U相、V相和W相开关元件组的通断状态的第一部分、第二部分和第三部分；将数字代码按照预定控制规则排列,形成第一数字代码序列,并将第一数字代码序列中的每个数字代码的第一部分、第二部分和第三部分中的约定的两个部分互换,形成第二数字代码序列；在第一和第二工作模式下,分别使用第一和第二数字代码序列对三相逆变器的各开关元件进行通断控制。通过本公开的逆变控制方法,能够便捷灵活且高效地实现电机的正反转。(The present disclosure provides an inversion control method applied to a three-phase inverter, the method including: compiling different on-off states of each switching element of the three-phase inverter in inversion control into digital codes, wherein each digital code sequentially comprises a first part, a second part and a third part corresponding to the on-off states of the U-phase, V-phase and W-phase switching element groups; arranging the digital codes according to a preset control rule to form a first digital code sequence, and interchanging two appointed parts of a first part, a second part and a third part of each digital code in the first digital code sequence to form a second digital code sequence; in the first and second operation modes, the switching elements of the three-phase inverter are controlled to be on and off by using the first and second digital code sequences, respectively. By the inversion control method, the forward and reverse rotation of the motor can be conveniently, flexibly and efficiently realized.)

1. An inversion control method is applied to a three-phase inverter and comprises the following steps:

compiling different on-off states of each switching element of the three-phase inverter in inversion control into digital codes, wherein each digital code sequentially comprises a first part, a second part and a third part corresponding to the on-off states of the U-phase, V-phase and W-phase switching element groups;

arranging the digital codes according to a preset control rule to form a first digital code sequence, and interchanging two appointed parts of a first part, a second part and a third part of each digital code in the first digital code sequence to form a second digital code sequence;

under a first working mode, on-off control is carried out on each switching element of the three-phase inverter by using a first digital code sequence; and in the second working mode, the switching elements of the three-phase inverter are controlled to be switched on and off by using a second digital code sequence.

2. The method of claim 1, wherein each of the digital codes in the first sequence of digital codes further comprises a fourth portion, the fourth portion being identical to the second portion and adjacent to the third portion, the first portion and the second portion of each digital code together forming one half-byte of the digital code, and the third portion and the fourth portion together forming the other half-byte of the digital code, then

A second sequence of digital codes is formed by interchanging the half byte of each digital code in the first sequence of digital codes with the other half byte; and

when the first/second digital code sequence is used for carrying out on-off control on each switch element, the U-phase switch element group, the V-phase switch element group and the W-phase switch element group are respectively carried out on-off control according to the first three parts of each digital code in the first/second digital code sequence.

3. The method of claim 1 or 2, wherein the predetermined control rules comprise arranging the digital codes in a manner corresponding in sequence to predetermined points of state change within one period on a target modulation waveform to form a first sequence of digital codes.

4. The method of claim 3, wherein the digital codes are arranged in sequential correspondence with predetermined points of state change within a period of the target modulation waveform to form:

wherein j is 1,2, …, (2n-6)/4, n is a predetermined number of switching angles, the arranged digital codes are spread to have 2n +1 digital codes corresponding to one sector in each row, the digital codes are arranged row by row in the left-to-right sequence to form a first digital code sequence, and a first half byte and a second half byte of each digital code in the first digital code sequence are interchanged to form a second digital code sequence.

5. The method of claim 4, further comprising:

calculating corresponding n switching angles by using a harmonic elimination equation set according to a given modulation degree, and respectively solving the switching angles of a U phase, a V phase and a W phase according to the n switching angles;

taking the switching angles in the first 60-degree domain of each phase of the three-phase switching angles, arranging the switching angles together from small to large, and taking the first n +1 switching angles from the arrangement result;

calculating n +1 duration times t according to the n +1 switching angles and the frequency of the target modulation waveform₁，t₂，…，t_n，t_n+1And the n +1 time durations are according to t₁，t₂，…，t_n-1，t_n，t_n+1，t_n，t_n-1，…，t₂，t₁Are sequentially assigned to 2n +1 digital codes corresponding to each sector in the first/second digital code sequence.

6. The method according to any one of claims 3 to 5, wherein a dead zone control code is provided in the first sequence of digital codes between each pair of adjacent digital codes for controlling the group of switching elements corresponding to the varying portion between each pair of adjacent digital codes to turn off for a preset duration Δ t.

7. The method of claim 6, wherein in the first digital code sequence, when a time interval between a pair of state change points corresponding to an adjacent pair of digital codes is less than or equal to Δ t, a previous digital code of the adjacent pair of digital codes is deleted from the first digital code sequence or a part of a duration of a digital code adjacent to the previous digital code is taken to compensate for the duration of the previous digital code.

8. The method of claim 1 or 2, wherein the predetermined control rule comprises arranging the digital codes in a voltage space vector combination manner to generate a first digital code sequence, which in turn comprises 6 sets of digital codes respectively corresponding to 6 space vector sectors.

9. The method of claim 8, wherein the voltage space vector combination comprises:

wherein j is (2n-6)/4, n is a predetermined number of switching angles, and the digital codes corresponding to the arranged voltage space vectors form a first digital code sequence from left to right and from top to bottom as a whole.

10. The method of claim 9, wherein during a period when a carrier frequency ratio of a target modulation waveform is higher than a predetermined value,

the voltage space vector combination corresponding to the first operating mode is:

the voltage space vector combination corresponding to the second operating mode is as follows:

11. the method according to any one of claims 8 to 10, wherein in each of the 6 sets of digital codes, a dead zone control code is provided between each pair of adjacent digital codes for controlling the group of switching elements corresponding to the changing portion between each pair of adjacent digital codes to be turned off for a preset duration.

12. The method of claim 8, wherein the voltage space vector combination comprises a seven-segment or five-segment voltage space vector combination,

in the case of a seven-segment voltage space vector combination:

the voltage space vector corresponding to the first working mode is combined into

The voltage space vector corresponding to the second working mode is combined into

In the case of a five-segment voltage space vector combination:

the voltage space vector corresponding to the first working mode is combined into

The voltage space vector corresponding to the second working mode is combined into

Where S1-S6 are 6 sectors of the voltage space vector.

Technical Field

The embodiment of the invention relates to the technical field of electricity, in particular to an inversion control method for controlling an inverter to work.

Background

The inverter is an electrical device that converts low-voltage direct current electric energy (such as 12V or 24V direct current voltage) into alternating current electric energy (such as 220V or 50HZ alternating current voltage), and is widely applied to various household appliances, electrical tools, lighting, electric vehicles, unmanned aerial vehicles and the like, for example, to drive motors in electric vehicles/unmanned aerial vehicles.

At present, the vector control (FOC) technology and the Direct Torque Control (DTC) technology are commonly adopted at home and abroad to realize the drive control of the motor. The vector control theory was proposed by doctor Hasse at university of Darmstader, germany in 1968, and systematically summarized and applied by f.blaschke at siemens, germany in 1971, and published in a patent form, which lays an important position of the theory in the field of inversion control. The direct torque control theory is successively proposed by a German scholark and a Japanese scholark Takahashi in the middle of 1980, and is a variable-voltage variable-frequency speed regulation technology of an alternating-current motor with high dynamic performance developed after a vector control technology.

As one of the most important leading technologies in this century, a driving motor controller in the new energy electric vehicle adopts the above-mentioned vector control (FOC) and Direct Torque Control (DTC) technologies in a theoretical level, and adopts a Digital Signal Processor (DSP) and a real-time calculation algorithm program in a practical level, wherein specific algorithms such as various coordinate transformations are also proposed by foreign scholars, and the national scholars only learn, track and improve the theoretical technologies.

At present, in domestic and foreign markets, no matter electric vehicles or unmanned aerial vehicles, the main motors are permanent magnet synchronous motors and asynchronous motors, and FOC and DTC are adopted for driving control. When the FOC and DTC technology is adopted for motor drive control, the following defects may exist:

1. the configured motor controller is difficult to perform off-line work and basically only can perform on-line work;

2. the configured motor controllers can only be applied one by one, so that the motor controllers are very sensitive to the change of motor parameters, are difficult to adapt to the same type of motor (the motor with the same rated voltage, rotating speed and power), and are difficult to adaptively optimize and control even the change of the parameters of the driven motor;

3. when the motor is driven, a sensor (an asynchronous motor needs a speed sensor, a synchronous motor needs a position/speed sensor) is required in the motor, and the normal working temperature of the motor is higher than 100 ℃, which brings great challenge to the reliability of the sensor, so that the failure rate of the electric vehicle is increased by about 10% due to the sensor (data provided by a certain electric vehicle manufacturer), and the FOC and the DTC are difficult to provide a universal and reliable method to solve the problem at present; meanwhile, the motor control schemes in the industry are all based on real-time calculation combined with DSP, but commercial DSP technology is limited abroad, and even if a high-speed DSP combined real-time calculation method is adopted, a sensor in the motor cannot be driven in a high-speed (high-frequency) or high-change rate (high speed or frequency change and large acceleration) situation.

In addition, when the FOC technology is used for driving a motor, a formula for generating a motor forward rotation driving signal is different from a formula for generating a motor reverse rotation driving signal, and complexity is high.

Disclosure of Invention

The invention provides an inversion control method aiming at the problems in the background art and aiming at reducing the complexity of motor driving and improving the reliability of the motor driving.

Therefore, the embodiment of the invention provides an inversion control method, which is applied to a three-phase inverter and comprises the following steps: compiling different on-off states of each switching element of the three-phase inverter in inversion control into digital codes, wherein each digital code sequentially comprises a first part, a second part and a third part corresponding to the on-off states of the U-phase, V-phase and W-phase switching element groups; arranging the digital codes according to a preset control rule to form a first digital code sequence, and interchanging two appointed parts of a first part, a second part and a third part of each digital code in the first digital code sequence to form a second digital code sequence; in the first working mode, the switching elements of the three-phase inverter are controlled to be switched on and off by using the first digital code sequence, and in the second working mode, the switching elements of the three-phase inverter are controlled to be switched on and off by using the second digital code sequence.

The invention has the beneficial effects that: by combining the preprocessing technology and the digital modulation technology, the forward rotation and the reverse rotation of the motor can be flexibly, conveniently and efficiently realized without the mode of combining a DSP with real-time calculation.

Drawings

In order that the invention may be more readily understood, it will be described in more detail with reference to specific embodiments thereof that are illustrated in the accompanying drawings. These drawings depict only typical embodiments of the invention and are not therefore to be considered to limit the scope of the invention.

FIG. 1A is an exemplary flow chart of an inversion control method according to one embodiment of the invention;

FIG. 1B is a schematic illustration of the numbering of the switching elements of a three-phase inverter according to an embodiment of the present invention;

FIG. 2A is an exemplary flow chart of an inversion control method according to another embodiment of the invention;

fig. 2B is a schematic numbering diagram of switching elements of a three-phase inverter according to another embodiment of the present invention.

Detailed Description

Embodiments of the present invention will now be described with reference to the drawings, wherein like parts are designated by like reference numerals. The embodiments described below and the technical features of the embodiments may be combined with each other without conflict.

Fig. 1A is an exemplary flowchart of an inversion control method according to an embodiment of the present invention, and fig. 1B is a number diagram of each switching element of a three-phase inverter according to an embodiment of the present invention. The inversion control method of the embodiment of the invention is used in the process of driving the motor by using the three-phase inverter.

As shown in fig. 1A, the inversion control method according to the embodiment of the present invention includes:

s01, compiling different on-off states of each switching element of the three-phase inverter in inversion control into digital codes, wherein each digital code sequentially comprises a first part, a second part and a third part corresponding to the on-off states of the U-phase, V-phase and W-phase switching element groups;

s02, arranging the digital codes according to a preset control rule to form a first digital code sequence;

s03, interchanging two appointed parts of the first part, the second part and the third part of each digital code in the first digital code sequence to form a second digital code sequence;

s04, in the first working mode, on-off control is carried out on each switching element of the three-phase inverter by using a first digital code sequence;

and S05, in the second working mode, on-off control is carried out on each switching element of the three-phase inverter by using the second digital code sequence.

In the present embodiment, the different on-off states of the switching elements of the three-phase inverter, which are present in the inverter control, are first compiled into digital codes. As shown in fig. 1B, the six switching elements of the U, V, W three arms of the three-phase inverter are named B0, B1, B2, B3, B4, and B5 in this order from bottom to top and from left to right, and the "on" state of the switching element is defined as 1 and the "off" state of the switching element is defined as 0. The switching state combinations that the six switching elements of the three-phase inverter exhibit during the inversion operation and the values of the digital code b5b4b3b2b1b0 corresponding to each combination are shown in table 1 below.

TABLE 1

b5

b4

b3

b2

b1

b0

b5b4b3b2b1b0

Closing device

Opening device

Closing device

Opening device

Closing device

Opening device

010101

Closing device

Opening device

Closing device

Opening device

Opening device

Closing device

010110

Opening device

Closing device

Closing device

Opening device

Closing device

Opening device

100101

Opening device

Closing device

Closing device

Opening device

Opening device

Closing device

100110

Closing device

Opening device

Opening device

Closing device

Closing device

Opening device

011001

Closing device

Opening device

Opening device

Closing device

Opening device

Closing device

011010

Opening device

Closing device

Opening device

Closing device

Closing device

Opening device

101001

Opening device

Closing device

Opening device

Closing device

Opening device

Closing device

101010

Each digital code b5b4b3b2b1b0 includes a first portion b1b0 corresponding to U-phase switching elements b1 and b0, a second portion b3b2 corresponding to V-phase switching elements b3 and b2, and a third portion b5b4 corresponding to W-phase switching elements b5 and b 4.

Then, the digital codes are arranged according to a preset inversion control rule to form a first digital code sequence. For example, digital codes corresponding to the respective state change points may be arranged in the order of each state change point of a target modulation waveform required to be output by the three-phase inverter to form a first digital code sequence, while a time interval between each pair of adjacent state change points is calculated as a switching element state duration (hereinafter referred to as a switching duration) corresponding to each digital code.

After the first digital code sequence is formed, converting the first digital code sequence to form a second digital code sequence, wherein the converting includes interchanging any two of the first portion, the second portion and the third portion of each digital code in the first digital code sequence, for example, interchanging the first portion b1b0 and the second portion b3b2 of each digital code in the first digital code sequence, interchanging the second portion b3b2 and the third portion b5b4 of each digital code in the first digital code sequence, or interchanging the first portion b1b0 and the third portion b5b4 of each digital code in the first digital code sequence. The switching duration corresponding to each digital code in the second sequence of digital codes may be the same as the switching duration corresponding to the corresponding digital code in the first sequence of digital codes.

In some embodiments of the present invention, after the first digital code sequence and the second digital code sequence are both formed, the first digital code sequence and the second digital code sequence may be preset as a control code sequence of the three-phase inverter, and the preprocessing stage is completed. In other embodiments of the present invention, after the first digital code sequence is formed, the first digital code sequence may also be preset as a control code sequence of the three-phase inverter, so as to complete the preprocessing stage.

In the actual working stage, a three-phase inverter is used for inverting the direct current power into alternating current power and outputting the alternating current power to the motor to drive the motor to run. According to the rotation direction of the motor, the operation mode of the motor can be divided into two modes of forward rotation and reverse rotation, and correspondingly, the three-phase inverter also has a first operation mode for outputting driving power for forward rotation of the motor and a second operation mode for outputting driving power for reverse rotation of the motor. In a first operating mode of the three-phase inverter, i.e. during the forward rotation of the electric machine, the switching elements of the three-phase inverter are switched using a first sequence of digital codes and corresponding switching durations. In a second operating mode, i.e. during the reversal of the electric machine, the switching elements of the three-phase inverter are switched using a second digital code sequence and the corresponding switching durations. In the embodiment that the first and second digital code sequences are preset in the preprocessing stage, the actual working stage is controlled by using the preset first digital code sequence and the preset second digital code sequence in the first working mode and the second working mode respectively; in the embodiment that only the first digital code sequence is preset in the preprocessing stage, the actual working stage is controlled by using the preset first digital code sequence in the first working mode, each digital code in the second digital code sequence is generated in real time according to each digital code in the first digital code sequence in the second working mode, and each digital code generated in real time is used for controlling.

In the embodiment of the invention, the first digital code sequence and the second digital code sequence are used for controlling the on-off of the three-phase inverter, so that the modulation degrees of the three-phase inverter can be kept consistent when the motor rotates forwards and reversely, the torque can be kept consistent when the motor rotates forwards and reversely, and the high stability of the operation of the motor is realized. Meanwhile, according to the scheme of the embodiment of the invention, the inversion control command does not need to be generated in real time according to the rotation direction of the motor rotor, so that the driving control of the motor by using the three-phase inverter can be realized without using a sensor in the motor.

Fig. 2A is an exemplary flowchart of an inversion control method according to another embodiment of the present invention, and fig. 2B is a number diagram of each switching element of a three-phase inverter according to another embodiment of the present invention.

As shown in fig. 2, the inversion control method according to the embodiment of the present invention includes:

s11, compiling different on-off states of the switching elements of the three-phase inverter in inversion control into digital codes, wherein each digital code sequentially comprises a first part, a second part, a third part and a fourth part corresponding to the on-off states of the switching element groups of the U-phase, the V-phase, the W-phase and the V' -phase, the first part and the second part of each digital code jointly form a half byte of the digital code, and the third part and the fourth part jointly form the other half byte of the digital code;

s12, arranging the digital codes according to a preset control rule to form a first digital code sequence;

s13, interchanging one half byte of each digital code in the first digital code sequence with the other half byte to form a second digital code sequence;

s14, in the first working mode, on-off control is carried out on each switching element of the three-phase inverter by using a first digital code sequence;

and S15, in the second working mode, on-off control is carried out on each switching element of the three-phase inverter by using the second digital code sequence.

In this embodiment, different on-off states of the switching elements of the three-phase inverter during the inversion control are compiled into digital codes. As shown in fig. 2B, six switching elements of U, V, W three arms of the three-phase inverter are named B0, B1, B2, B3, B4 and B5 in sequence from bottom to top and from left to right, and unlike the embodiment shown in fig. 1A to 1B, in this embodiment, a virtual arm of one phase is added to the equivalent circuit diagram of the three-phase inverter, and the switching state of the virtual arm is consistent with that of the V-phase arm, so that the virtual arm is named as a "V ' -phase arm", the V ' -phase arm is placed behind the W-phase arm, and two switches in the V ' -phase arm are named as B7 and B6 from top to bottom. In the present embodiment, the virtual V' phase arm does not exist in the actual circuit, and digital encoding is performed by the virtual arm for inverter control. Similarly, the "on" state of the switching element is defined as 1, and the "off" state of the switching element is defined as 0. Thus, the switching state combinations exhibited by the eight switching elements shown in fig. 2B during the inversion operation and the values of the digital codes B7B6B5B4B3B2B1B0 corresponding to each combination are shown in table 2 below.

TABLE 2

b7

b6

b5

b4

b3

b2

b1

b0

b7b6b5b4b3b2b1b0

16 carry system

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Opening device

Closing device

Opening device

Closing device

Opening device

Closing device

Opening device

01010101

55

Closing device

Opening device

Closing device

Opening device

Closing device

Opening device

Opening device

Closing device

01010110

56

Closing device

Opening device

Opening device

Closing device

Closing device

Opening device

Closing device

Opening device

01100101

65

Closing device

Opening device

Opening device

Closing device

Closing device

Opening device

Opening device

Closing device

01100110

66

Opening device

Closing device

Closing device

Opening device

Opening device

Closing device

Closing device

Opening device

10011001

99

Opening device

Closing device

Closing device

Opening device

Opening device

Closing device

Opening device

Closing device

10011010

9A

Opening device

Closing device

Opening device

Closing device

Opening device

Closing device

Closing device

Opening device

10101001

A9

Opening device

Closing device

Opening device

Closing device

Opening device

Closing device

Opening device

Closing device

10101010

AA

Each digital code b7b6b5b4b3b2b1b0 includes a first portion b1b0 corresponding to U-phase switching elements b1 and b0, a second portion b3b2 corresponding to V-phase switching elements b3 and b2, a third portion b5b4 corresponding to W-phase switching elements b5 and b4, and a fourth portion b7b6 corresponding to V' -phase switching elements b7 and b 6. The first b1b0 and second b3b2 portions of each digital code together form a half byte b3b2b1b0 of the digital code, and the third b5b4 and fourth b7b6 portions together form the other half byte b7b6b5b4 of the digital code.

Then, the digital codes are arranged according to a preset inversion control rule to form a first digital code sequence. For example, digital codes corresponding to the respective state change points may be arranged in the order of each state change point of a target modulation waveform required to be output by the three-phase inverter to form a first digital code sequence, while a time interval between each pair of adjacent state change points is calculated as a switching element state duration (hereinafter referred to as a switching duration) corresponding to each digital code.

After the first digital code sequence is formed, the first digital code sequence is converted to form a second digital code sequence. In this embodiment, the conversion is specifically to interchange the first half byte b7b6b5b4 and the second half byte b3b2b1b0 of each digital code in the first digital code sequence, and the conversion process may be performed in a preset stage or in real time in an actual working stage.

The switching duration corresponding to each digital code in the second digital code sequence in this embodiment may also be the same as the switching duration corresponding to the corresponding digital code in the first digital code sequence.

In this embodiment, similar to the embodiment shown in fig. 1A, the presetting of the first digital code sequence or the presetting of the first and second digital code sequences may be performed in a preprocessing stage, and the second digital code sequence may be generated in real time or controlled using the preset first and second digital code sequences in an actual working stage. In this embodiment, since each digital code includes a fourth encoded portion corresponding to the on-off state of the V '-phase virtual bridge arm switching element, and the V' -phase bridge arm does not actually exist in the three-phase inverter, when the first/second digital code sequence is used to actually control the on-off of each switching element of the three-phase inverter in the first/second operation mode, the U-phase, V-phase, and W-phase switching element groups are respectively controlled on-off according to the first, second, and third portions of each digital code in the first/second digital code sequence, and the fourth portion of each digital code is ignored.

In the embodiment of the invention, the virtual bridge arm V' with one phase consistent with the switching state of the V phase is added to the equivalent circuit diagram of the three-phase inverter, so that the formed control digital code for the forward rotation of the motor is very convenient to convert into a control digital code sequence for the reverse rotation of the motor, and meanwhile, the modulation degree of the three-phase inverter can be kept consistent when the motor rotates forward and reversely, thereby the torque is kept consistent when the motor rotates forward and reversely, and the high stability of the operation of the motor is realized.

In the above embodiment, when the digital codes are arranged according to the predetermined inversion control rule, the digital codes may be arranged according to the order of the state change points of the target modulation waveform required to be output by the three-phase inverter to form the first digital code sequence, specifically, the state change points in one complete cycle on the target modulation waveform may be ordered on the time axis, and the digital codes corresponding to the state change points may be arranged in sequence to form the first digital code sequence. The manner of determining the state change points on the target modulation waveform may include, for example, performing calculations by a known computer program to obtain different combinations of state change points, and a detailed description thereof is omitted here.

In an embodiment of the present invention, an improved combination of state change points on a target modulation waveform is provided, and an array obtained by arranging digital codes according to the combination of the state change points is given below (wherein, for simplicity, the digital codes in the following embodiments are all represented by 16 systems):

wherein n is the number of the preset switching angles, and can be specifically set according to actual requirements. The digital codes in the array are arranged in the order from left to right and from top to bottom to form a first digital code sequence.

For example, when n is 7, j is 2, the array may be written as:

that is, the portion of the array labeled j repeats once.

Formula (1.1), which has been developed from formula (1), can also be represented in the form of the following table 3-1:

TABLE 3-1

S1	56	66	AA	66	56	55	65	66	56	55	65	66	AA	66	65
																S2	66	65	55	65	66	AA	A9	65	66	AA	A9	65	55	65	A9
S3	65	A9	AA	A9	65	55	99	A9	65	55	99	A9	AA	A9	99
																S4	A9	99	55	99	A9	AA	9A	99	A9	AA	9A	99	55	99	9A
S5	99	9A	AA	9A	99	55	56	9A	99	55	56	9A	AA	9A	56
																S6	9A	56	55	56	9A	AA	66	56	9A	AA	66	56	55	56	66

S1-S6 in table 3-1 indicate 6 sectors within a 360 ° domain (one sector per 60 ° domain).

Arranging the array as a whole from left to right and from top to bottom to form a first digital code sequence: (56, 66, AA, 66, 56, 55, 65, 66, 56, 55, 65, 66, AA, 66, 65, 66, 65, 55, 65, …, AA, 9A, 56, 55, 56, 9A, AA, 66, 56, 55, 56, 66), the second digital code sequence may be formed by interchanging the front and rear parts of each digital code in the first digital code sequence, or the second digital code sequence may be formed by first interchanging the front and rear parts of each digital code in the digital array in the above formula (1.1) or the above table 3-1 and then arranging the whole in the order from left to right and from top to bottom to form the second digital code sequence in substantially the same manner as the first digital code sequence and then converting.

For another example, when n is 5, j is 1, the array may be written as:

that is, the portion of the array labeled j appears only once.

Similarly, equation (1.2), which has been expanded from equation (1), may also be expressed in tabular form similar to Table 3-1, as shown in Table 3-2 below:

TABLE 3-2

S1	56	66	AA	66	56	55	65	66	AA	66	65
												S2	66	65	55	65	66	AA	A9	65	55	65	A9
S3	65	A9	AA	A9	65	55	99	A9	AA	A9	99
												S4	A9	99	55	99	A9	AA	9A	99	55	99	9A
S5	99	9A	AA	9A	99	55	56	9A	AA	9A	56
												S6	9A	56	55	56	9A	AA	66	56	55	56	66

Arranging the whole digital code array from left to right and from top to bottom to form a first digital code sequence: (56, 66, AA, 66, 56, 55, 65, 66, AA, 66, 65, 66, 65, 55, 65, …, AA, 9A, 56, 55, 56, 9A, AA, 66, 56, 55, 56, 66) and the second digital code sequence may be formed by interchanging the front and rear portions of each digital code in the first digital code sequence.

In one embodiment of the present invention, n +1 durations may be set for 2n +1 digital codes per line in the above equation (1) to achieve that the target modulation waveform is a sine wave. The durations set for the 2n +1 digital codes of each line are respectively: t is t₁、t₂、…、t_n-1、t_n、t_n+1、t_n、t_n-1、…、t₂、t₁Wherein, t₁、t₂、…t_nAnd t_n+1Satisfies 6X (2t₁+2t₂+……+2t_n+t_n+1) T is the period of the fundamental wave of the sine wave to be output by the three-phase inverter, the switching frequency of the three-phase inverter is 2(c-1)/T, c is the number of the durations which need to be stored, and c is n + 1.

For example, duration t may be correspondingly allocated to each line of digital codes in equation (1.2)₁、t₂、t₃、t₄、t₅、t₆、t₅、t₄、t₃、t₂、t₁The following formula (1.2.1) is obtained (below which the corresponding duration mark of each numerical code is located, and formula (1.2.1) can also be expressed in tabular form like table 3):

wherein, t₁、t₂、t₃、t₄、t₅And t₆Satisfies 6 × (2 t)₁+2t₂+2t₃+2t₄+2t₅+t₆) T is the period of the fundamental wave of the sine wave to be output by the three-phase inverter, and the switching frequency of the three-phase inverter is 2(c-1)/T, in which embodiment c is 6.

In another embodiment of the present invention, the elimination of higher harmonics in the output sine wave can also be achieved by assigning the switching angle calculation duration to the corresponding digital code in the sequence of digital codes. Specifically, first, there is the following formula according to the harmonic elimination method:

wherein, α_iN is the number of switching angles, and k is 1,2, …, (n-3)/2.

When n is odd, the harmonic amplitude A_6k-1And A_6k+1Is 0, modulation degree m>0 and upper limit of m<1 (linear modulation is performed when the upper limit of m is between 0.94 and 0.99 according to the value of n, for example, 0 is performed when n is 5<m<0.99; when n is 15, 0<m<0.96) and the distribution of the switching angles is 0<α₁<α₂<…<α_n-2<60°<α_n-1<α_n<At 90 deg., a set of digital code arrays independent of modulation degree m is given (e.g., equation (1) above), and corresponding n switching angles are calculated using harmonic cancellation equations (2.1), (2.2), (2.3) according to the given modulation degree m. And respectively obtaining the switching angles of the U phase, the V phase and the W phase according to the n switching angles, taking the switching angles in the first 60-degree domain of each phase of the three-phase switching angles, arranging the switching angles from small to large together, taking the first n +1 switching angles from the arrangement result, calculating n +1 duration times t according to the n +1 switching angles and the frequency of a target modulation waveform, and distributing the duration times t to corresponding digital codes in a first digital code sequence obtained by the given digital code array irrelevant to the modulation degree m and corresponding digital codes in a second digital code sequence obtained by converting the first digital code sequence.

Specifically, firstly, a modulation degree m is given according to a required target modulation waveform, and the equations (2.1), (2.2) and (2.3) are solved to obtain n switching angles α corresponding to the modulation degree m₁、α₂、…、α_n。

The switching angle in the 360 DEG domain of the U-phase is then solved α₁、α₂、…、α_n、180°-α_n、180°-α_n-1、…、180°-α₁、180°+α₁、180°+α₂、…、180°+α_n、360°-α_n、360°-α_n-1、…、360°-α₁The switching angle of the U phase is shifted forward by 240 degrees to obtain a switching angle of the V phase α_n-1-60°、α_n-60°、120°-α_n、120°-α_n-1、…、120°-α₁、120°+α₁、120°+α₂、…、120°+α_n、300°-α_n、300°-α_n-1、…、300°-α₁Then, the U-phase switching angle is shifted forward by 120 degrees to obtain the W-phase switching angle of 60- α_n、60°-α_n-1、…、60°-α₁、60°+α₁、60°+α₂、…、60°+α_n、240°-α_n、240°-α_n-1、…、240°-α₁、240°+α₁、240°+α₂、…、240°+α_n。

Considering the symmetry of the sine wave, the switching angles for each phase U, V, W take only the following switching angles in the first 60 ° domain:

and (4) phase U: 0<Uα₁、Uα₂、…、Uα_n1<60°，n1<n；

Phase V: 0<Vα₁、Vα₂、…、Vα_n2<60°，n2<n；

Phase W: 0<Wα₁、Wα₂、…、Wα_n3<60°，n3<n；

The switching angles in the three groups of 60-degree domains are uniformly arranged into a UVW switching angle β numerical sequence of 0<β₁<β₂<…<β_n1+n2+n3Taking the first n +1 UVW switching angles of the array, and calculating n +1 duration time T according to the following formula according to the period T of the sine wave required to be output₁、t₂、…、t_n、t_n+1：

A specific example is given below, where the modulation degree m is 0.5 and the number n of the switching angles is 9, then solving equations (2.1), (2.2), and (2.3) yields α as 9 switching angles corresponding to the modulation degree 0.5₁＝2.43，α₂＝13.07，α₃＝21.36，α₄＝25.58，α₅＝33.23，α₆＝38.03，α₇＝45.23，α₈＝62.64，α₉＝69.61。

The switching angles in the three-phase 60 ° domain are then determined U, V, W as follows:

and (4) phase U: 2.43, 13.07, 21.36, 25.58, 33.23, 38.03, 45.23;

phase V: 2.64, 9.61, 50.39, 57.36;

phase W: 14.78, 21.97, 26.78, 34.42, 38.64, 46.93, 57.57.

The three groups of 18 switch angles are sorted according to size to form a number sequence: (2.43, 2.64, 9.61, 13.07, 14.78, 21.36, 21.97, 25.58, 26.78, 33.23, 34.42, 38.03, 38.64, 45.23, 46.93, 50.39, 57.36, 57.57), taking the first n +1, i.e., the first 10 switching angles of the sequence: (2.43, 2.64, 9.61, 13.07, 14.78, 21.36, 21.97, 25.58, 26.78 and 33.23), and the frequency of the sine wave to be output by the three-phase inverter is set to be 100Hz, the period T is 10000 mus, and the 10 duration T can be calculated according to the above formula (3)₁-t₁₀Respectively as follows: 67.6,5.8, 193.6, 96.0, 47.5, 182.8, 17.1, 100.3, 33.1, 179.2.

Meanwhile, taking the numerical code array of the above formula (1) as an example, if j is 3 can be calculated according to n being 9, the above formula (1) can be written as follows:

then 10 duration times t calculated according to the same n value₁-t₁₀Assigning each digital code in equation (1.3), with the duration mark below it, in a similar manner as in equation (1.2.1), results in the duration-assigned digital code array in table 4 below:

TABLE 4

When the digital code arrays in table 4 above are arranged in the order from left to right and from top to bottom, a first digital code sequence is obtained, and the respective digital codes in the first digital code sequence are used to perform on-off control of the respective switching elements of the three-phase inverter for the corresponding durations in table 4, that is, a three-phase sine wave having a modulation degree of 0.5 and the first 28 th harmonics eliminated can be output. Similarly, a second digital code sequence is obtained by interchanging the front and rear halves of each digital code in the first digital code sequence for controlling the three-phase inverter to output power for reversing the motor.

In the invention, the scheme is defined as a Harmonic elimination digital Code Modulation (HEDM) technology, and the applicant has successfully developed three-phase inverter chips with different frequencies (50Hz, 60Hz, 400Hz, 500Hz and 1000Hz) based on the technology, and the three-phase inverter chips are applied to different industries and are approved by customers. The 14-pin three-phase 50Hz/60Hz chip HT3156IA can be applied to an interactive UPS or EPS, the modulation degree is 0.58-1.13, the harmonic elimination times are 2-250 times/50 Hz and 2-214 times/60 Hz, the voltage stabilization precision of the output fundamental wave voltage is less than 2%, the frequency precision is less than 0.1%, and the protection functions of soft start, overcurrent, overvoltage, undervoltage, fault shutdown and the like are realized; the modulation degree of a 14-pin three-phase 400Hz chip HT3400M is 0.7-1.145, the harmonic elimination frequency is 2-70 times under the modulation degree of 0.7-0.9, 2-58 times under the modulation degree of 0.905-1.025, 2-46 times under the modulation degree of 1.03-1.145, the output voltage regulation rate is less than 1%, the output frequency precision is less than 0.1%, and the chip has the functions of soft start/variable frequency start selection, current detection, fault control, positive and negative rotation selection and the like. Particularly, the two frequency conversion chips HT33400YM and HT33800SM have output fundamental wave frequencies of 3Hz-400Hz and 3Hz-800Hz respectively, and the modulation degree is 0.05-1.17, and the two chips have the common characteristic that the HEDM technology is integrated in a chip with only 28 pins, so that the self-adaptive control of a 4-pole asynchronous motor non-speed sensor and an 8-pole permanent magnet synchronous motor non-position sensor is realized; the total number of sine waves (same frequency, different modulation degrees, same modulation degree and different frequencies) output by the two chips exceeds 1 ten thousand, the harmonic frequency within 10KHz is eliminated by the fundamental wave frequency after 20Hz, the harmonic heating of the motor is greatly reduced, the four-phase four-pole asynchronous/8-pole permanent magnet synchronous variable frequency motor is suitable for any 4-pole asynchronous/8-pole permanent magnet synchronous variable frequency motor, and is irrelevant to the motor parameter of drive control and the change of the parameter, and the driven electric automobile can be in the optimal drive state through self-adaptive control no matter the driven electric automobile is in the processes of acceleration, deceleration, cruising or starting. Particularly, the chip HT33400YM has been applied to electric vehicles, and the chip 33800SM has been subjected to design verification on an electric vehicle simulation test platform.

In some embodiments of the present invention, a dead zone control code may be provided between each pair of adjacent digital codes in the first digital code sequence, the dead zone control code being for controlling the group of switching elements corresponding to the changing portion between each pair of adjacent digital codes to turn off for a preset duration t. The changing part between the adjacent digital codes has two conditions, one is that the switching state of one of U, V, W three bridge arms is changed, and the other is that the switching state of two of U, V, W three bridge arms is changed.

Taking the 16-ary coded digital codes adopted in the embodiment shown in fig. 2A-2B as an example (the dead zone control code can be analogized when the binary digital code of the embodiment shown in fig. 1A-1B is adopted), the relationship between the adjacent digital codes of the three-phase bridge arm with the changed switch state can be seen in the following table 5-1, and the relationship between the adjacent digital codes of the three-phase bridge arm with the changed switch states can be seen in the following table 5-2:

watch 5-1 (Single bridge arm change)

TABLE 5-2 (two arms change)

In order to protect the switching elements, in this embodiment, when the switching state of the bridge arm is to be changed, the two switching elements of the bridge arm to be changed are turned off for a certain time to be buffered, and then the two switching elements are switched to the switching state that is changed, so as to ensure that the two switching elements of the same bridge arm are not turned on at the same time. The present embodiment implements dead-zone protection of the switching elements of the three-phase inverter by adding a dead-zone control code between two adjacent digital codes and setting a corresponding dead-zone time.

Continuing with the example of a digital code in 16-ary form comprising four portions corresponding to U, V, W, V 'phases, a total of 18 dead band control codes can be determined, as shown in tables 5-3 below, according to the definition of dead band control codes, U, V (V' same), switching elements of one or two phase legs in W phase are all in the off state:

tables 5 to 3

Binary system	16 carry system	Binary system	16 carry system	Binary system	16 carry system
						00010010	12	00010001	11	00000001	01
00100001	21	00100010	22	00000010	02
						01000110	46	01000101	45	00010000	10
01100100	64	01010100	54	00100000	20
						10001001	89	10001010	8A	01000100	44
10011000	98	10101000	A8	10001000	88

As shown in table 5-3, the encoding method of the dead zone control code is the same as the encoding method of the digital code, and the dead zone control code is also a digital code. The addition of each of the dead band control codes shown in table 5-3 between the varying adjacent numerical codes as shown in tables 5-1 and 5-2 may be as shown in tables 5-4 and 5-5:

watch 5-4 (Single bridge arm change)

Tables 5-5 (two arms change)

In the following, a specific example is given by taking the state change of a single bridge arm as an example, and the state change of two bridge arms is similar to this.

Referring to the allocation of the dead zone control codes between adjacent digital codes in table 5-4, a corresponding dead zone control code is added between every two adjacent digital codes in the digital code array shown in table 3-2, as shown in table 5-4-1 below (for clarity, the dead zone control codes are underlined in the table):

TABLE 5-4-1

S1	56	46	66	22	AA	22	66	46	56	54	55	45	65	64	66	22	AA	22	66	64	65	64
																							S2	66	64	65	45	55	45	65	64	66	22	AA	A8	A9	21	65	45	55	45	65	21	A9	21
S3	65	21	A9	A8	AA	A8	A9	21	65	45	55	11	99	89	A9	A8	AA	A8	A9	89	99	89
																							S4	A9	89	99	11	55	11	99	89	A9	A8	AA	8A	9A	98	99	11	55	11	99	98	9A	98
S5	99	98	9A	8A	AA	8A	9A	98	99	11	55	54	56	12	9A	8A	AA	8A	9A	12	56	12
																							S6	9A	12	56	54	55	54	56	12	9A	8A	AA	22	66	46	56	54	55	54	56	46	66	46

The first digital code sequence is obtained by arranging the digital code arrays in the above table 5-4-1 in the order from left to right and from top to bottom, and the second digital code sequence is obtained by interchanging the front and rear halves of each digital code (including the dead zone control code) in the first digital code sequence. And the dead zone control can be realized during the inversion control of the three-phase inverter by using each digital code in the first/second digital code sequence to control the on-off of each switching element of the three-phase inverter.

With this embodiment, it is not necessary to use a hardware circuit to control the dead time period, and the reliability of the inverter circuit can be greatly improved.

In the case of performing the three-phase inverter control with dead zone control, the duration of each dead zone control code in table 5-4-1 may be set to be Δ t, and the original duration t minus Δ t of each digital code is used as the actual duration of the digital code in the three-phase inverter control with dead zone control. For example, for the numerical code of equation (1.2.1), the original duration t₁、t₂、t₃、t₄、t₅、t₆Accordingly becomes t₁-Δt、t₂-Δt、t₃-Δt、t₄-Δt、t₅-Δt、t₆-Δt。

In some embodiments of the present invention, in the first digital code sequence, when a time interval between a pair of state change points corresponding to an adjacent pair of digital codes is less than or equal to the duration Δ t of the dead zone control code, a previous digital code of the adjacent pair of digital codes may be deleted from the first digital code sequence. In other words, the duration time allocated to the previous digital code of the adjacent pair of digital codes is very short, even shorter than the duration time Δ t of the dead zone control code, in which case the digital code having the shorter duration time may be deleted in order to improve the accuracy of the inversion control.

In an alternative embodiment of the present invention, in the first digital code sequence, when the time interval between a pair of state change points corresponding to an adjacent pair of digital codes is less than or equal to the duration Δ t of the dead zone control code, a previous digital code in the adjacent pair of digital codes may not be deleted, and a part of the duration of the digital code adjacent to the previous digital code may be taken to compensate for the duration of the previous digital code, and the length of the part may be greater than the duration Δ t of the dead zone control code when the sum of the duration of the previous digital code and the duration of the previous digital code is greater.

Again using equation (1.2.1) as an example, assume 6 durations t₁、t₂、t₃、t₄、t₅、t₆T in (1)₂Less than or equal to the duration of the dead band control code at, the first digital code sequence corresponding to t may be deleted for improved control accuracy₂The digital codes in column 2 and column 2 of table 5-4-1 are deleted, and meanwhile, the dead zone control codes (the adjusted dead zone control codes are marked by bold fonts) connected between the original column 1 and column 3 and between the original column 1 and column 3 are adjusted according to the distribution mode of the dead zone control codes between adjacent digital codes in table 5-4, so as to obtain the digital code array with dead zone control codes (marked by dashed lines) as shown in the following table 5-4-2:

TABLE 5-4-2

Meanwhile, in order not to affect the cycle of the sine wave to be output, the original duration of the deleted digital code may be added to the duration of the immediately adjacent digital code of the deleted digital code. In the present embodiment, the original duration of the deleted digital code is t₂Taking the 18 digit codes in the first row in table 5-4-2, i.e. the sector S1, the duration allocated to the 18 digit codes after the duration adjustment is, from left to right, respectively: t is t₁+t₂-Δt、Δt、t₃-Δt、Δt、t₄-Δt、Δt、t₅-Δt、Δt、t₆-Δt、Δt、t₅-Δt、Δt、t₄-Δt、Δt、t₃-Δt、Δt、t₁+t₂-Δt、Δt。

The above embodiments have exemplified the case where the predetermined control rule is used to arrange the digital codes according to the state change points on the target modulation waveform to form the first digital code sequence, but the present invention is not limited thereto. In other embodiments of the present invention, the predetermined control rule may further include an equal area method, a voltage space vector method, and the like, and the voltage space vector method is specifically described below.

The voltage space vector method is used as a preset control rule to arrange the digital codes according to a voltage space vector combination mode to generate a first digital code sequence, wherein the first digital code sequence sequentially comprises 6 groups of digital codes respectively corresponding to 6 space vector sectors.

According to the definition of voltage space vector (refer to 'variable frequency speed control system of permanent magnet synchronous motor and its control', Yuanchang et al), there are 8 voltage space vectors U₀[000]、U₁[001]、U₂[010]、U₃[011]、U₄[100]、U₅[101]、U₆[110]、U₇[111]According to the on-off states of the three-phase bridge arm switching elements corresponding to the 8 voltage space vectors, the 8 voltage space vectors and the 8 16-system digital codes shown in table 2 can be mapped in a one-to-one correspondence manner, as shown in table 6 below.

TABLE 6

The conventional seven-segment voltage space vector combination shown in table 7-1 below is used as an example, and the seven-segment voltage space vector shown in table 7-1 can be mapped into a digital code form according to the mapping relationship between the voltage space vector and the digital code shown in table 6, as shown in table 7-2 below.

TABLE 7-1

Sector area	Seven segment voltage space vector	Sector area	Seven segment voltage space vector
				S1	U0 U4 U6 U7 U6 U4 U0	S4	U0 U1 U3 U7 U3 U1 U0
S2	U0 U2 U6 U7 U6 U2 U0	S5	U0 U1 U5 U7 U5 U1 U0
				S3	U0 U2 U3 U7 U3 U2 U0	S6	U0 U4 U5 U7 U5 U4 U0

TABLE 7-2

For ease of explanation, the voltage space vector shown in Table 7-1 will be referred to as the seven-segment first voltage space vector.

The digitally-coded three-phase inversion control based on the voltage space vector control rule can be realized by arranging the digital code combinations shown in table 7-2 in the sector sequence to form a first digital code sequence corresponding to the forward rotation of the motor, interchanging the front and rear halves of each digital code in the formed first digital code sequence (for example, converting the digital code 65 into 56) to form a second digital code sequence corresponding to the reverse rotation of the motor, and performing inversion control on the three-phase inverter by using the first digital code sequence and the second digital code sequence, and the present embodiment greatly simplifies the three-phase inversion control based on the voltage space vector control rule, particularly in the inversion control during the reverse rotation of the motor, the voltage vector calculation formula adopted during the reverse rotation of the motor in the conventional voltage space vector inversion control is even different from the voltage vector calculation formula adopted during the forward rotation of the motor, in the embodiment, only the second digital code sequence generated by converting the first digital code sequence is used for three-phase inversion control during the motor inversion control, so that the control method is greatly simplified, and the inversion control in the voltage space vector-based inversion control, particularly the inversion control during the motor inversion, is well improved.

In addition, the digital code combinations for forward rotation of the motor in table 7-2 can be exchanged by the front nibble and the rear nibble of each digital code to form the digital code combinations for reverse rotation of the motor in table 7-3:

tables 7 to 3

In the embodiment of the invention, the seven-segment digital code combination in the table 7-3 can be reversely mapped into the voltage space vector combination in the table 7-4 according to the corresponding relation shown in the table 6, and can be directly used for voltage vector control during the motor reverse rotation. For convenience of explanation, the voltage space vector shown in table 7-4 will be referred to as a seven-segment second voltage space vector.

Tables 7 to 4

During the operation of the motor controlled by using the seven-segment first voltage space vector shown in table 7-1 and the seven-segment second voltage space vector shown in table 7-4, respectively, the operation direction of the motor is opposite, but the frequency and the torque of the output are the same. A specific example is illustrated in tables 7-5 below, where the duration sequence of each sector vector is shown in units of 62.5ns, with a period of 0.333s, a frequency of 3Hz, and a modulation of about 2x (230+250)/(2500+230+250+5000+250+230+2500) to 0.088. The time duration sequence of tables 7-5 was verified for operation on a three-phase asynchronous motor having a pole pair number of 2 indicating that the motor outputs the same torque and frequency during positive and negative rotation control using the first and second seven-stage voltage space vectors shown in tables 7-1 and 7-4, respectively.

Tables 7 to 5

In some embodiments of the present invention, digitally coded three-phase inversion control based on voltage space vector control rules may also incorporate dead-zone control. As an example, with reference to the allocation manner of the dead zone control codes between the adjacent digital codes in table 5-4, in each of the 6 sectors in table 7-2, a dead zone control code is provided between each pair of adjacent digital codes for controlling the switching element group corresponding to the change portion between each pair of adjacent digital codes to be turned off for a preset dead zone duration Δ t when the adjacent digital codes are switched. After the dead zone control codes are added, the digital code array shown in table 7-2 is converted into the form shown in table 7-6 below (in which the dead zone control codes are underlined for clarity):

tables 7 to 6

Sector area	Seven-segment digital code and dead zone control code
		S1	55 54 56 12 9A 8A AA 8A 9A 12 56 54 55
S2	55 11 99 98 9A 8A AA 8A 9A 98 99 11 55
		S3	55 11 99 89 A9 A8 AA A8 A9 89 99 11 55
S4	55 45 65 21 A9 A8 AA A8 A9 21 65 45 55
		S5	55 45 65 64 66 22 AA 22 66 64 65 45 55
S6	55 54 56 46 66 22 AA 22 66 46 56 54 55

The digital code combinations shown in tables 7-6 are arranged according to the sector sequence to form a first digital code sequence corresponding to the forward rotation of the motor, front and back half parts of each digital code in the first digital code sequence are interchanged (namely, front and back half parts of each dead zone control code in the first digital code sequence are also interchanged) to form a second digital code sequence corresponding to the reverse rotation of the motor, and the first digital code sequence and the second digital code sequence are used for carrying out inversion control on the three-phase inverter, so that the voltage space vector control rule-based digital coded three-phase inversion control with dead zone control can be realized. In this embodiment, the duration of the dead zone control code may be set arbitrarily, and accordingly, the duration of the dead zone control code is subtracted from the original duration of the digital code adjacent to the dead zone control code to obtain the available duration. With this embodiment, it is not necessary to use a hardware circuit to control the dead time period, and the reliability of the inverter circuit can be greatly improved.

The above is given an example based on the mapping of the seven-segment first voltage space vector into the digital code array and the formation of the first digital code sequence in sequence and the conversion into the second digital code sequence as shown in table 7-1, but the present invention is not limited to the mapping of the seven-segment voltage space vector, and other types of voltage space vector combinations may be mapped into the digital code with reference to the above-mentioned method, and dead zone control codes, such as the case of the five-segment voltage space vector combination mentioned in the aforementioned reference, may be further set.

In addition, the invention also provides several improved voltage space vector combinations to further realize better technical effect. In order to better understand the technical effect of the improved voltage space vector combination proposed by the present invention, the characteristics of the conventional seven-segment and five-segment voltage space vector combinations will be briefly described.

The seven-segment and five-segment voltage space vector combinations are the vector combinations mainly used in the industry at present, wherein the seven-segment voltage space vector combinations can be seen in the table 7-1, and the five-segment voltage space vector combinations can be seen in the table 8-1. For convenience of explanation, the voltage space vector shown in FIG. 8-1 will be referred to as a five-segment first voltage space vector.

TABLE 8-1

Sector area	Five segment voltage space vector	Sector area	Five segment voltage space vector
				S1	U4 U6 U7 U6 U4	S4	U3 U1 U0 U1 U3
S2	U6 U2 U0 U2 U6	S5	U1 U5 U7 U5 U1
				S3	U2 U3 U7 U3 U2	S6	U5 U4 U0 U4 U5

The five-segment voltage space vector shown in table 8-1 may be mapped into a digital code form, as shown in table 8-2 below:

TABLE 8-2

Sector area	Five-segment digital code	Sector area	Five-segment digital code
				S1	56 9A AA 9A 56	S4	A9 65 55 65 A9
S2	9A 99 55 99 9A	S5	65 66 AA 66 65
				S3	99 A9 AA A9 99	S6	66 56 55 56 66

The digitally-coded three-phase inversion control based on the voltage space vector control rule can be realized by arranging the digital code combinations shown in table 8-2 in a sector sequence to form a first digital code sequence corresponding to the forward rotation of the motor, interchanging the front half part and the rear half part of each digital code in the formed first digital code sequence (for example, converting the digital code 65 into 56) to form a second digital code sequence corresponding to the reverse rotation of the motor, and performing inversion control on the three-phase inverter by using the first digital code sequence and the second digital code sequence.

Further, similarly to the case of the seven-segment voltage space vector combination, the digital code combinations for motor forward rotation in table 8-2 may also be subjected to the front and rear nibble interchange of each digital code to form the digital code combinations for motor reverse rotation in table 8-3:

tables 8 to 3

Sector area	Five-segment digital code (reverse)	Sector area	Five-segment digital code (reverse)
				S1	65 A9 AA A9 65	S4	9A 56 55 56 9A
S2	A9 99 55 99 A9	S5	56 66 AA 66 56
				S3	99 9A AA 9A 99	S6	66 65 55 65 66

Similarly, the combination of five pieces of digital codes of table 8-3 can also be reverse-mapped to the combination of voltage space vectors shown in table 8-4 according to the correspondence shown in table 6, and can be directly used for voltage vector control during motor reverse rotation. For convenience of explanation, the voltage space vector shown in fig. 8-4 will be referred to as a fifth-segment second voltage space vector.

Tables 8 to 4

Sector area	Five segment voltage space vector	Sector area	Five segment voltage space vector
				S1	U1 U3 U7 U3 U1	S4	U6 U4 U0 U4 U6
S2	U3U2 U0 U2 U3	S5	U4 U5 U7 U5 U4
				S3	U2 U6 U7 U6 U2	S6	U5 U1 U0 U1 U5

The five-segment and seven-segment voltage space vector combinations exemplified above are run alternately counter-clockwise and clockwise. For example, in the case of a seven-segment voltage space vector combination, the odd sectors operate predominantly counterclockwise (e.g., U first)₄→U₆Then is U₆→U₄) Clockwise operation is auxiliary; the even sectors are mainly clockwise (e.g. U first)₂→U₆Then is U₆→U₂) And the anticlockwise operation is auxiliary. The motor torque is easily fluctuated due to the overlarge readjustment amplitude during the auxiliary operation, especially when the motor is used for the low-speed control of the asynchronous motor.

To this end, in one embodiment of the present invention, an improved voltage space vector combination is proposed, and the voltage space vector combination of the following formula (4.1) can be mapped to the above formula (1) according to the mapping relationship between the voltage space vector and the digital code shown in table 6:

meanwhile, after the first and second halves of each digital code in the digital code array of the above formula (1) are exchanged, the voltage space vector and the digital code are mapped to the voltage space vector combination of the following formula (4.2) according to the mapping relationship shown in table 6:

wherein, each line of digital codes corresponds to one sector and totally corresponds to six sectors. n is the number of the preset switch angles, when n takes different values, the numerical value of j is different, and the expressions (4.1) and (4.2) can be expanded in different modes according to the different values of j. Equations (4.1) and (4.2) can be directly used in the voltage space vector control method as an improved voltage space vector combination, where equation (4.1) is used for vector control during forward rotation of the motor and equation (4.2) is used for vector control during reverse rotation of the motor. Alternatively, the voltage space vectors of equations (4.1) and (4.2) may be mapped back to the corresponding digital codes and form the first digital code sequence and the second digital code sequence in the order from left to right and from top to bottom as a whole.

The vector combinations of the formulas (4.1) and (4.2) each include three parts (each part is marked by a middle bracket), and the former part of the three parts can be called a head vector, the middle part can be called a main vector, and the latter part can be called a tail vector. When the carrier frequency ratio (the ratio of the carrier frequency to the fundamental frequency) is high in the inverter control, energy is transferred mainly through the primary vector, during which the head and tail vectors in equations (4.1) and (4.2) can be removed and abbreviated in the form of the following table 9-1 and table 9-2, and for convenience of explanation, the voltage space vector shown in table 9-1 is referred to as a four-segment first voltage space vector, and the voltage space vector shown in table 9-2 is referred to as a four-segment second voltage space vector:

TABLE 9-1

Sector area	Four-segment type main vector	Sector area	Four-segment type main vector
				S1	U1 U0 U4U5	S4	U6 U7 U3 U2
S2	U5 U7 U6 U4	S5	U2 U0 U1 U3
				S3	U4 U0 U2 U6	S6	U3 U7 U5 U1

TABLE 9-2

Sector area	Four-segment type main vector	Sector area	Four-segment type main vector
				S1	U4 U0 U1 U5	S4	U3 U7 U6 U2
S2	U5 U7 U3 U1	S5	U2 U0 U4 U6
				S3	U1 U0 U2 U3	S6	U6 U7 U5 U4

The four-stage first voltage space vector of table 9-1 is used for vector control during forward rotation of the motor, and the four-stage second voltage space vector of table 9-2 is used for vector control during reverse rotation of the motor.

Taking the four-stage first voltage space vector of table 9-1 (and so on for the four-stage second voltage space vector of table 9-2), the cycle output of the vector in each sector is mainly counterclockwise, and clockwise callback is auxiliary, and when switching between sectors, that is, when cycling through S1 → S2 → S3 → S4 → S5 → S6 → S1, the output is counterclockwise and no clockwise output, so that the operation of the control motor is very smooth. Meanwhile, by adopting the four-segment type first and second voltage space vectors shown in tables 9-1 and 9-2, control is easier to realize than the seven-segment type first and second voltage space vectors shown in tables 7-1 and 7-4 and the five-segment type first and second voltage space vectors shown in tables 8-1 and 8-4, and particularly when switching the motor operation direction, the control is not required to be recalculated by using another formula, but only the four-segment type main vector shown in tables 9-1 and 9-2 is required to be switched.

In the embodiment of the present invention, the four-segment first and second voltage space vectors shown in tables 9-1 and 9-2 may also be combined with the dead zone control codes of the foregoing embodiments, specifically, in each group of vectors (or digital codes corresponding to vectors) corresponding to 6 groups of digital codes of 6 sectors, a dead zone control code is provided between each pair of adjacent vectors (or digital codes) for controlling the switch element group corresponding to the change portion between each pair of adjacent vectors (or digital codes) to be turned off within a preset duration. The manner in which the dead zone control code is added can be referred to the foregoing embodiments. With the addition of the dead zone control code, the four-stage first and second voltage space vectors shown in tables 9-1 and 9-2 can be represented in a fully digital coded form (omitted here) similar to that shown in tables 7-3, or in a form in which the dead zone control code is added between adjacent vectors in tables 9-3 and 9-4 below (where the dead zone control code is underlined for differential display):

tables 9 to 3

Sector area	Four-segment type main vector	Sector area	Four-segment type main vector
				S1	U1 45 U0 54 U4 46 U5 22	S4	U6 8A U7 A8 U3 89 U2 11
S2	U5 22 U7 8A U6 12 U4 54	S5	U2 11 U0 45 U1 21 U3 A8
				S3	U4 54 U0 11 U2 98 U6 8A	S6	U3 A8 U7 22 U5 64 U1 45

Tables 9 to 4

Sector area	Four-segment type main vector	Sector area	Four-segment type main vector
				S1	U4 54 U0 45 U1 64 U5 22	S4	U3 A8 U7 8A U6 98 U2 11
S2	U5 22 U7 A8 U3 21 U1 45	S5	U2 11 U0 54 U4 12 U6 8A
				S3	U1 45 U0 11 U2 89 U3 A8	S6	U6 8A U7 22 U5 46 U4 54

In addition to the above-mentioned state change point rule and voltage space vector rule, the digital coding technique of the present invention can be combined with other inversion control rules to implement digital inversion control, such as field oriented vector control (FOC) and Direct Torque Control (DTC) of a Permanent Magnet Synchronous Motor (PMSM), and these two techniques can also be combined with the digital coding technique of the present invention to implement forward and reverse rotation control of motors with the same measurement (same frequency and torque) by using the same data table and algorithm, so that the design of control software is highly simplified, and the reliability is greatly improved.

The above-described embodiments are merely preferred embodiments of the present invention, and general changes and substitutions by those skilled in the art within the technical scope of the present invention are included in the protection scope of the present invention.