CN101599704B - Space vector modulating method for reducing narrow-pulse phenomenon of matrix converter - Google Patents

Abstract

The invention discloses a space vector modulation method for reducing the narrow pulse phenomenon of a matrix converter, which is characterized in that: when the minimum value of the switching state duration of four effective vectors in a certain modulation period is less than twice the commutation time , three zero vector modulations are used in the modulation period, that is, they are added before the first effective vector, between the second and third effective vectors, and after the fourth effective vector, and their sum is equal to the total duration T0 of zero vectors. On the premise of not changing the duration of the effective space vector, the present invention fundamentally avoids the phenomenon of narrow pulses caused by the duration of the switch state being shorter than the commutation time, solves the problem of output waveform distortion caused by narrow pulses, and greatly improves low-profile The quality of the output waveform of the matrix converter and the range of low-voltage voltage regulation during system ratio. When no narrow pulse appears, the traditional modulation method is still used to reduce switching loss and ensure high modulation ratio requirements. The invention only needs to adjust the modulation mode of the space vector, and the method is simple and easy.

Description

A Space Vector Modulation Method for Reducing the Narrow Pulse Phenomenon of Matrix Converter

technical field

The invention belongs to the technical field of AC power conversion devices, in particular to a control method of a three-phase matrix converter of space vector modulation, so as to avoid or reduce output waveform distortion caused by PWM narrow pulse phenomenon.

Background technique

The three-phase matrix converter 1 is composed of nine bidirectional power switches 2 in the form of a 3×3 switch matrix, as shown in FIG. 1 . where S _{i, j} (i=A, B, C; j=a, b, c) represents a bidirectional power switch 2, each bidirectional power switch consists of two insulated gate bipolar transistors (IGBTs) with antiparallel diodes ) is composed of a "common emitter" structure. The input side of the matrix converter is the three-phase grid voltage 3, denoted by u _a , u _b , u _c respectively, and there is an input filter 4 indirectly between the matrix converter and the grid. The output sides of the matrix converter are denoted by A, B, and C respectively, and are usually connected to an AC motor or an inductive load device 5 . Through on-off control of nine bidirectional power switches, an output voltage with variable amplitude and frequency can be realized.

The 9 bidirectional power switches have a total of 27 switching states, which are usually represented by a group of three letters. For example: abb, it means that the first output phase A of the matrix converter is connected to the input phase a through the bidirectional switch S _Aa , the second output phase B is connected to the input phase b through the bidirectional switch S _Bb , and the third output phase C is connected through the bidirectional switch S Aa Switch S _Cb is connected to input phase b. The 27 switch states correspond to 24 effective space vectors and 3 zero vectors. According to the basic modulation principle of space vector, there are 5 switching states in each modulation cycle, which generate 4 effective space vectors and 1 zero vector respectively.

According to the space vector of the input current and the space vector of the expected output voltage, the 5 switching states and the corresponding duty ratios d _αm , d in each modulation cycle can be determined by the direct space vector or indirect space vector modulation strategy of the matrix converter _αn , d _βn , d _βm , d ₀ (or duration T _αm , T _αn , T _βn , T _βm , T ₀ ). Then, according to the modulation sequence of the five switch states and the duration of the switch states, the turn-on and turn-off of the nine bidirectional power switches can be controlled to realize the control of the matrix converter. Usually, the modulation sequence of the 5 switch states is arranged according to the minimum number of switch switching.

When the five switching states of the matrix converter are switched, that is, when the output phase is switched from one input phase to another, a commutation strategy must be adopted to strictly follow the commutation steps to turn off and turn on the corresponding power switches to ensure The input phase is not short-circuited and the output phase is not open-circuited during the commutation process. The time required for commutation (commutation time) T _h depends on the commutation steps used and the turn-on and turn-off times of the power switching devices. When the duration of a bidirectional power switch state calculated according to the space vector modulation strategy is less than the commutation time _Th , the bidirectional power switch forms a PWM narrow pulse. If the narrow pulse is not processed, the commutation logic will be confused .

Taking the output line voltage space vector and the input current space vector in one sector as an example, the bidirectional power switch states that generate four effective space vectors are abb, aab, aac, acc, respectively. Figure 2 is a schematic diagram of narrow pulse formation. Fig. 2a, Fig. 2b and Fig. 2c respectively show nine bidirectional power switch PWM modulation diagrams when the zero vector is post-positioned, zero-vector pre-positioned and zero-vector mid-positioned, where T ₁ =T _αm , T ₂ =T _αn , T ₃ =T _βn , T ₄ =T _βm is the duration of the effective space vector switching state. In Figure 2a, when T ₁ < 2T _h , the modulation pulse of the bidirectional power switch S _Bb is a narrow pulse, or when (T ₁ + T ₂ ) < 2T _h , the bidirectional power switches S _Cb and S _Cc form a narrow pulse , or (T ₂ +T ₃ )<2T _h , the bidirectional power switch S _Ba will also form a narrow pulse, but when T ₄ <T _h will not generate a narrow pulse. Similarly, in Figure 2b, when T ₄ <T _h or (T ₂ +T ₃ )<2T _h or (T ₃ +T ₄ )<T _h , a narrow pulse will be formed, and when T ₁ <2T _h , No narrow pulses are generated. In FIG. 2c, when T ₁ <2T _h or (T ₁ +T ₂ )<2T _h or T ₄ <T _h or (T ₃ +T ₄ )<T _h , a narrow pulse will be formed.

To sum up, no matter how the zero vector is placed in the modulation strategy with 5 switching states, once min(T ₁ , T ₂ , T ₃ , T ₄ )≤2T _h , it is possible to form a narrow pulse. If the narrow pulses are not properly processed, there will be a chaotic situation where the current commutation process is not over and the next commutation process will start, resulting in a matrix converter input short circuit or output open circuit.

Usually the narrow pulse is dealt with by discarding the narrow pulse switching state or extending the pulse width to the commutation time T _h . Although the two methods avoid commutation faults, discarding or increasing the pulse width will cause output voltage distortion. Especially when the matrix converter works at a low modulation ratio, the probability of narrow pulses is extremely high, and the resulting distortion of the output waveform increases rapidly. When the modulation ratio is lower than 0.2, the quality of the output waveform cannot meet the requirements.

Hidenori Hara et al. in 2005 in the paper "Improvement of output voltage control performance for low-speed operation of matrix converter", (Improvement of output voltage control performance of matrix converter under low-speed conditions) (IEEE transactions on powerelectronics, Vol.20, NO .6, November 2005) proposed a narrow pulse processing method for the matrix converter of dual voltage modulation, and avoided the narrow pulse phenomenon by properly splitting the output vector, but did not give a solution for the matrix converter of space vector modulation.

Contents of the invention

The purpose of the present invention is to address the shortcomings of traditional space vector modulation techniques, and propose a space vector modulation method that reduces the narrow pulse phenomenon of the matrix converter, which can avoid or greatly reduce the output waveform caused by the narrow pulse phenomenon Distortion problem.

The space vector modulation method for reducing the narrow pulse phenomenon of the matrix converter provided by the present invention is characterized in that when the minimum value of the switching state duration of the four effective vectors in any modulation period T _s is less than the commutation time T _h When twice that of , three zero-vector modulations are used in the modulation period, that is, zeros of three different switch states are added before the first effective vector, between the second and third effective vectors, and after the fourth effective vector. vector, the sum of the three zero-vector durations is equal to the total zero-vector duration T ₀ .

In the traditional space vector modulation method, only one zero vector is used, and there are 5 switching states in each modulation period, and the narrow pulse phenomenon is inevitable. The present invention adopts three different zero-vector modulation methods when narrow pulses may appear, and there are seven switching states in each modulation cycle. Since the total duration T ₀ of the zero vector is very long when the modulation ratio is low (T ₀ is equal to the modulation period T _s minus the sum of the duration of all effective vectors), it is divided into three zero vectors and inserted into the effective space vector, without changing the effective Under the premise of the space vector duration (T ₁ , T ₂ , T ₃ , T ₄ ), it is equivalent to widening the modulation pulse width of the bidirectional power switch, fundamentally avoiding the problem caused by the duration of the switch state being shorter than the commutation time The narrow pulse phenomenon solves the problem of output waveform distortion caused by narrow pulses, and greatly improves the output waveform quality and low-voltage voltage regulation range of the matrix converter at low modulation ratios. When there is no narrow pulse (usually high modulation ratio), the traditional modulation method of 5 switching states is still used to reduce switching loss and ensure high modulation ratio requirements.

The present invention does not use a compensating method to compensate the distortion of the output waveform, so it does not need to add additional hardware circuits and controls, and only needs to adjust the modulation mode of the space vector, and the method is simple and easy.

Description of drawings

Figure 1 is a topology diagram of a three-phase matrix converter.

Figure 2 is a schematic diagram of narrow pulse formation.

Fig. 3 is a flow chart of the implementation method of the present invention.

Figure 4 shows the space vector modulation method based on three zero vectors.

FIG. 5 shows the principle of avoiding narrow pulses in the modulation method of the present invention.

Fig. 6 is an implementation schematic diagram of an example provided by the present invention.

Fig. 7 is the output waveform after implementing the present invention.

Detailed ways

The present invention provides a modulation method based on space vector modulation matrix converter to avoid narrow pulse phenomenon, which adopts three zero-vector modulation and traditional modulation mixed modulation methods, and its purpose is to meet the requirements while avoiding or reducing the narrow pulse phenomenon. High modulation ratio requirements and reduced bidirectional power switching losses.

The present invention will be described in more detail below by means of examples and drawings, but the following examples are only illustrative, and the protection scope of the present invention is not limited by these examples. As shown in Figure 3, the implementation steps of this example include:

(1) According to the traditional space vector modulation principle, determine the switching states of the four effective vectors in each modulation period T _s , and calculate the duty ratios d _αm , d _αn , d _βn , d _βm of the four switching states.

(2) According to the principle of optimizing the switching times, the modulation order of the four switching states, the corresponding duration T ₁ , T ₂ , T ₃ , T ₄ , and the total duration T ₀ of the zero vector are obtained,

When the sum of the output voltage sector and the input current sector is an even number,

T ₁ =d _αm T _s

T ₂ =d _αn T _s

T ₃ =d _βn T _s

T ₄ =d _βm T _s

T ₀ =T _s -T ₁ -T ₂ -T ₃ -T ₄

When the sum of the output voltage sector and the input current sector is an odd number,

T ₁ =d _αn T _s

T ₂ =d _αm T _s

T ₃ =d _βm T _s

T ₄ =d _βn T _s

T ₀ =T _s -T ₁ -T ₂ -T ₃ -T ₄

(3) Judging whether the minimum value of T ₁ , T ₂ , T ₃ and T ₄ is less than twice the commutation time Th _h , if it is less than 2T _h , it indicates that a narrow pulse may appear, enter (4) using three zero vectors Modulation method, otherwise enter (7) to adopt the traditional modulation method. _Th is the commutation time.

(4) Judging whether T ₀ is greater than or equal to 5T _h , if the condition is satisfied, enter (5) adopt the modulation method of three zero vectors to avoid the narrow pulse, if not, enter (6) process the narrow pulse by discarding or extending the method.

(5) In order to avoid narrow pulse phenomenon, insert 3 different zero-vector switch states in the modulation cycle, and the selection of the inserted 3 zero-vector switch states is selected according to the principle that only one bidirectional power switch is changed from the front and rear switch states , that is, three zero vectors of different switch states are added before the first effective vector, between the second and third effective vectors, and after the fourth effective vector, using such a modulation method without changing the duration T ₁ , T ₂ , T ₃ , and T ₄ , it is equivalent to widening the modulation pulse width of the bidirectional power switch. The durations corresponding to the three zero vectors are respectively T ₀₁ , T ₀₂ , T ₀₃ ,

2T _h ≤ T ₀₂ =T ₀₁ ≤(T ₀ -T _h )/2, T ₀₃ =(T ₀ -T ₀₁ -T ₀₂ ).

In order to reduce the output common-mode voltage, it is suggested that: T ₀₁ =T ₀₂ =2T _h , T ₀₃ =(T ₀ -T ₀₁ -T ₀₂ ).

Still taking the output voltage space vector and the input current space vector both in one sector as an example, three zero vectors bbb, aaa and ccc are inserted respectively, and the seven switching states and the modulation sequence are bbb-abb-aab-aaa-aac-acc - ccc, Fig. 4 shows the 7 switching states and modulation sequences based on the present invention, and Fig. 5 shows the principle of avoiding the phenomenon of narrow pulses in the modulation method of the present invention. It can be clearly seen from Fig. 5 that when three zero-vector switching states are inserted, and each zero-vector duration T ₀₁ , T ₀₂ , and T ₀₃ are calculated according to the method of the present invention, objectively the duration of each bidirectional power switch T ₀₁ or T ₀₂ or T ₀₃ is added, so that even if the duration of any one of T ₁ , T ₂ , T ₃ , and T ₄ is shorter than the commutation time, it can ensure that the duration of each bidirectional power switch is longer than the commutation time , there will be no narrow pulse phenomenon.

The present invention requires that the modulation strategy of three zero vectors can only be adopted when T ₀ ≥ 5T _h , in order to ensure that the bidirectional power switches corresponding to the three zero vectors do not generate narrow pulses.

The research found that under the condition of T _s = 200μs, T _h = 4μs, the modulation ratio is in the range of 0-0.862, min(T ₁ , T ₂ , T ₃ , T ₄ ) < 2T _h , and T ₀ ≥ The probability of 5T _h is 100%. As the modulation ratio increases, the probability of t ₀ ≥ 5T _h decreases. When the modulation ratio is 0.866, min(T ₁ , T ₂ , T ₃ , T ₄ )<2T _h appears , and the probability of T ₀ ≥ 5T _h is 94.4%. Studies have shown that within the range of modulation ratio 0-0.862, the use of three zero-vector modulation methods can completely avoid the narrow pulse phenomenon; when the modulation ratio is higher than 0.862, most of the narrow pulse phenomena can be avoided by three zero-vector modulation methods. When the modulation ratio is 0.866, 94.4% of the narrow pulses can be avoided by three zero-vector modulation methods, and only 5.6% of the cases cannot use three zero-vector modulation, and the narrow pulses need to be discarded or extended. Because the modulation ratio is very high, no matter whether the narrow pulse is discarded or extended, the distortion of the output waveform caused by it is quite inconspicuous.

(6) When T ₀ <5T _h , recalculate T ₁ , T ₂ , T ₃ , and T ₄ by using the processing method of extending the narrow pulse.

Extend the durations of T ₁ , T ₂ , T ₃ , and T ₄ that are less than 2T _h to not less than 2T _h . The extended time should be subtracted from other durations greater than 2T _h . After recalculation, each duration should be T ₁ +T ₂ +T ₃ +T ₄ +T ₀ =T _s is satisfied.

(7) Set one of T ₀₁ , T ₀₂ , and T ₀₃ as T ₀ , and the remaining two values as 0, and then adopt the traditional five switching states (T ₁ , T ₂ , T ₃ , T ₄ , T ₀ ) modulation method for modulation. T ₀₁ , T ₀₂ , T ₀₃ can be calculated according to one of the following methods:

Method 1: 1 zero vector preposition, T ₀₁ ＝T ₀ , T ₀₂ ＝T ₀₃ ＝0

Method 2: Set one zero vector in the middle, T ₀₂ ＝T ₀ , T ₀₁ ＝T ₀₃ ＝0

Method 3: 1 zero vector postposition, T ₀₃ ＝t ₀ , T ₀₂ ＝T ₀₁ ＝0

If the voltage-type commutation strategy is adopted, it is recommended to adopt the modulation method 2 with the zero vector in the middle (for the reason, please refer to the invention patent 200720088237.5).

(8) The commutation control circuit arranges the on and off of the nine bidirectional power switches of the matrix converter according to the state modulation sequence and duration of the bidirectional power switches to realize the commutation control.

The implementation of the mixed modulation method of the above-mentioned 3 zero vectors is shown in Figure 6, wherein steps (1) and (2) are realized by digital signal processor DSP TMS320LF2407, and the control program is written in assembly language, steps (3)-(8) Realized by Field Programmable Gate Array FPGA EP2C8T144C8, wherein step (8) commutation control circuit control program is a prior art.

The above-mentioned modulation method for avoiding the narrow pulse phenomenon has been verified experimentally on a matrix converter with an inductive load circuit device, and a good effect of reducing output waveform distortion has been achieved. Under the working condition of a low modulation ratio of 0.0866, the output current waveform of the matrix converter adopting the traditional 5 switch state modulation and the hybrid modulation method of the present invention is shown in FIG. 7 . Figure 7a shows the current waveform using a zero-vector center modulation method. In order to avoid the narrow pulse phenomenon, the method of extending the narrow pulse width equal to the commutation time T _h is adopted, and the output current waveform is seriously distorted. Figure 7b is the current waveform of mixed modulation using 3 zero vectors and 1 zero vector in the middle. It can be seen that the modulation method of the present invention can avoid or reduce the output waveform distortion caused by the narrow pulse phenomenon, especially very good It improves the output waveform of the matrix converter in the case of low modulation ratio.

The present invention is not limited to the above-mentioned specific embodiments, and those skilled in the art can implement the present invention by using other various specific embodiments according to the disclosed content of the embodiments and accompanying drawings. Some simple changes or modified designs all fall within the protection scope of the present invention.

Claims (2)

1. A space vector modulation method that reduces the narrow pulse phenomenon of the matrix converter, is characterized in that, when the minimum value in the switching state duration of four effective vectors in any modulation cycle T _s is less than the commutation time T _h When twice that of , three zero-vector modulations are used in the modulation period, that is, three zero-vectors with different switching states are added before the first effective vector, between the second and third effective vectors, and after the fourth effective vector , the sum of the three zero-vector durations is equal to the total zero-vector duration T ₀ . 2. space vector modulation method according to claim 1, is characterized in that, the concrete realization step of this method comprises: The first step is to determine the switching states of the 4 effective vectors in each modulation period T _s according to the traditional space vector modulation principle, and calculate the duty ratios d _αm , d _αn , d _βn , d _βm corresponding to the 4 switching states; In the second step, according to the principle of optimizing the number of switches, the modulation order of the four switch states is obtained; at the same time, the corresponding durations T ₁ , T ₂ , T ₃ , T ₄ are calculated using the following formula (I) or (II) respectively, and Zero vector total duration T ₀ , When the sum of the output voltage sector and the input current sector is an even number, $\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;m</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\\ {\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;n</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\\ {\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;n</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\\ {\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;m</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\\ {\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; )</span>$ When the sum of the output voltage sector and the input current sector is an odd number, $\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;n</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\\ {\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;m</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\\ {\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;m</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\\ {\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;n</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\\ {\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; II</span>}<span\; class="notranslate">\; )</span>$ The third step is to judge whether the minimum value among T ₁ , T ₂ , T ₃ and T ₄ is less than twice the commutation time T _h , if yes, go to step 4, otherwise go to step 7; The fourth step is to judge whether T ₀ is greater than or equal to 5T _h , if the condition is met, go to step 5, if not, go to step 6; In the fifth step, three zero vectors of different switching states are added before the first effective vector, between the second and third effective vectors, and after the fourth effective vector, and then enter the eighth step; Step 6 Recalculate T ₁ , T ₂ , T ₃ , and T ₄ by using the processing method of extending the narrow pulse, and the durations obtained after recalculation satisfy T ₁ +T ₂ +T ₃ +T ₄ +T ₀ =T _s , and then go to step 8; Step 7 Set the duration corresponding to the three zero vectors as T ₀₁ , T ₀₂ , T ₀₃ according to the switching order, set one of T ₀₁ , T ₀₂ , T ₀₃ as T ₀ , and the remaining two The value is 0, and then the traditional 5 switch state modulation method is used for modulation; The eighth step is to arrange the turn-on and turn-off of each bidirectional power switch in the matrix converter according to the state modulation sequence and duration of the bidirectional power switch, so as to realize the commutation control.

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