阅读说明：本技术 一种双级式矩阵变换器低压下的共模电压抑制策略 (common mode voltage suppression strategy under low voltage of two-stage matrix converter ) 是由 公铮 李景杰 朱凯 苏大汇 戴鹏 李康 张为国 于 2019-09-26 设计创作，主要内容包括：本发明公开了一种双级式矩阵变换器低压下的共模电压抑制策略,基于新的双级式矩阵变换器拓扑,其拓扑结构是在传统双级式矩阵变换器的直流侧上、下母线各串联一个IGBT开关管；本发明采用新的双空间矢量调制策略,当逆变级零矢量作用期间时,关断直流侧开关管,当逆变级有效矢量作用期间,导通直流侧开关管,同时根据整流级扇区的奇偶性,将逆变级空间矢量组合分为两种,依据不同空间矢量组合重新划分逆变级扇区,在每个扇区内选择相邻的有效矢量和零矢量合成期望输出电压矢量。本发明的有益之处是相较于现有共模电压抑制策略,输入输出电流质量良好,在电压传输比从0～0.5区域内将负载侧共模电压进一步抑制到传统调制策略的0.371倍；整流级能够实现零换流,换流控制简单,提高了系统可靠性。(The invention discloses a common-mode voltage suppression strategy of a two-stage matrix converter under low voltage, which is based on a new two-stage matrix converter topology, wherein the topology structure is that an IGBT switching tube is respectively connected in series with an upper bus and a lower bus on the direct current side of the traditional two-stage matrix converter; the invention adopts a new double-space vector modulation strategy, switches off a direct current side switch tube during the action period of an inverter level zero vector, switches on the direct current side switch tube during the action period of an inverter level effective vector, simultaneously divides the inverter level space vector combination into two types according to the parity of a rectifier level sector, re-divides the inverter level sector according to different space vector combinations, and selects adjacent effective vectors and zero vectors in each sector to synthesize an expected output voltage vector. Compared with the existing common mode voltage suppression strategy, the common mode voltage suppression method has the advantages that the quality of input and output currents is good, and the common mode voltage on the load side is further suppressed to be 0.371 times of that of the traditional modulation strategy in a voltage transmission ratio range from 0-0.5; the rectification stage can realize zero current conversion, the current conversion control is simple, and the system reliability is improved.)

1. the common-mode voltage suppression strategy under the low voltage condition of the two-stage matrix converter is characterized in that a new two-space vector modulation strategy is adopted to further suppress the load side common-mode voltage under the low voltage condition based on a new two-stage matrix converter topology.

2. The strategy for suppressing the common-mode voltage at the low voltage of the two-stage matrix converter as claimed in claim 1, wherein the new double space vector modulation strategy keeps the conventional current space vector modulation of the rectifier stage unchanged, then controls the on and off of the dc-side switch tube, and changes the space vector modulation of the inverter stage according to different sectors of the rectifier stage as follows:

(1) The inverter stage adopts a seven-segment space vector modulation strategy, and when the inverter stage is in a zero vector action period, the direct current side switching tube is switched off; when the inverter stage effective vector acts, the direct-current side switch tube is conducted;

(2) According to the parity of the sector of the rectification stage, the space vector combination of the inversion stage is divided into two types; v₁representing 100, three numbers sequentially represent the switch states of three bridge arms of the inverter stage A, B, C from left to right, 1 represents the conduction of an upper bridge arm switch, 0 represents the conduction of a lower bridge arm switch, and similarly, V₂Represents 110, V₃Is represented by 010, V₄Represents 011, V₅Represents 001, V₆Represents 101; v₀Represents 000, V₇represents 111; when the sectors of the rectifying stage are odd, the inverter stage adopts V₁ V₃ V₅And V₀Involving vector synthesis as a valid vector and a zero vector, V₁ V₃ V₅The inversion stage is divided into three sectors, and two adjacent effective vectors and a zero vector V are adopted in each sector₀To synthesize a desired voltage vector; when the sectors of the rectifier stage are even numbers, the inverter stage adopts V₂ V₄ V₆And V₇Involving vector synthesis as a valid vector and a zero vector, V₂ V₄ V₆The inversion stage is also divided into three sectors, and two adjacent effective vectors and a zero vector V are adopted in each sector₇To synthesize the desired voltage vector.

3. The strategy of claim 1, wherein the duty cycle of the inverter stage effective vector action is solved as follows:

The expected input current vector is synthesized by two adjacent effective current vectors, and the effective current vectors have duty ratios of d_a、d_bDesired output voltageThe vector is synthesized by two adjacent effective voltage vectors and a zero vector, and the duty ratios of the effective voltage vectors and the zero vector are d respectively_m、d_n、d₀The formula is as follows:

In the formula: theta_cFor the sector angle of the rectifier stage, theta_vFor the inversion stage sector angle, m_vThe inverse level modulation ratio.

Technical Field

The invention relates to a common-mode voltage suppression technology of a power electronic converter, in particular to a common-mode voltage suppression strategy of a two-stage matrix converter under low voltage.

Background

The two-stage matrix converter is a novel AC-AC converter, not only has the advantages of sine input and output currents, bidirectional energy flow, no need of a DC energy storage element, high power density, compact structure and the like of the traditional matrix converter, but also has the advantages of rectification zero current conversion, simple control of a clamping circuit and the like, and has great development potential. During the past 20 years, the study has attracted the attention of numerous scholars at home and abroad.

in the motor driving application, a load side of the two-stage matrix converter can generate common-mode voltage, so that shaft current is formed, a motor bearing is damaged, the service life of a motor is shortened, and meanwhile, the common-mode voltage can generate the common-mode current in a system to cause electromagnetic interference to the normal operation of the device.

The existing literature carries out relevant research on common-mode voltage suppression of a two-stage matrix converter, one method is to avoid that an inverter stage directly uses a zero vector to participate in synthesis of an expected voltage vector to realize suppression of the common-mode voltage, for example, a modulation strategy that a rectifier stage has a zero vector, the inverter stage uses two effective vectors with opposite directions to replace the zero vector, and the like, the methods can suppress the common-mode voltage to 0.577 times of that of a traditional modulation strategy in a voltage transmission ratio of 0-0.5 region, but the method directly causes that the rectifier stage needs to adopt a four-step current conversion strategy, the control is complex, the defect of increasing the switching frequency exists, the system loss is increased, and the harmonic distortion rate of input and output currents is increased; the other method is to change the distribution position of sectors of the rectifier stage, synthesize intermediate direct-current voltage by using two smaller line voltages, synthesize an expected voltage vector by using two effective vectors and a zero vector in the inverter stage, suppress the common-mode voltage to 0.577 times of the traditional modulation strategy in the voltage transmission ratio range of 0-0.5, and simultaneously, because the inverter stage has the zero vector, if the inverter stage adopts a seven-segment switching sequence, the rectifier stage can realize zero-current commutation, but the actual switching times are greatly increased, and if the seven-segment switching sequence is not adopted, the rectifier stage must adopt a four-step commutation strategy. In summary, the conventional modulation strategy for suppressing the common mode voltage has the lowest value of the common mode voltage suppression which is 0.577 times that of the conventional modulation strategy in the voltage transmission ratio of 0-0.5, and has the disadvantages of more or less complicated commutation of the rectifier stage, increased switching times and the like.

Disclosure of Invention

the invention aims to realize the maximum suppression of the common-mode voltage of a two-stage matrix converter in a voltage transmission ratio range of 0-0.5 and realize the zero current commutation of a rectifier stage on the premise of ensuring the quality of input and output electric energy.

The technical scheme adopted by the invention is as follows:

a common-mode voltage suppression strategy under low voltage of a two-stage matrix converter is based on a new two-stage matrix converter topology, and a new double-space vector modulation strategy is adopted to suppress common-mode voltage.

The new topology of the two-stage matrix converter is composed of a rectification stage, a direct current side and an inverter stage, wherein the rectification stage is a three-phase bridge circuit formed by combining six bidirectional switch units, each bidirectional switch is formed by connecting two IGBTs of a common-emitter stage in series, a unidirectional switch tube is respectively connected in series on a direct current upper bus and a direct current lower bus, a switch tube emitter of the upper bus is connected with the inverter stage, a switch tube emitter of the lower bus is connected with the rectification stage, and the inverter stage is a three-phase bridge circuit formed by combining six unidirectional switch tubes.

The new double space vector modulation strategy is to keep the traditional current space vector modulation of the rectifier stage unchanged, then control the on and off of the direct current side switching tube, and change the space vector modulation of the inverter stage according to different sectors of the rectifier stage, specifically as follows:

(1) The inverter stage adopts a seven-segment space vector modulation strategy, and when the inverter stage is in a zero vector action period, the direct current side switching tube is switched off; when the inverter stage effective vector acts, the direct-current side switch tube is conducted;

(2) according to the sector of the rectifier stageThe parity of (2) divides the inverse level space vector combination into two types; v₁Representing 100, three numbers sequentially represent the switch states of three bridge arms of the inverter stage A, B, C from left to right, 1 represents the conduction of an upper bridge arm switch, 0 represents the conduction of a lower bridge arm switch, and similarly, V₂Represents 110, V₃Is represented by 010, V₄Represents 011, V₅Represents 001, V₆Represents 101; v₀Represents 000, V₇represents 111; when the sectors of the rectifying stage are odd, the inverter stage adopts V₁ V₃ V₅And V₀Involving vector synthesis as a valid vector and a zero vector, V₁ V₃ V₅The inversion stage is divided into three sectors, and two adjacent effective vectors and a zero vector V are adopted in each sector₀To synthesize a desired voltage vector; when the sectors of the rectifier stage are even numbers, the inverter stage adopts V₂ V₄ V₆And V₇involving vector synthesis as a valid vector and a zero vector, V₂ V₄ V₆the inversion stage is also divided into three sectors, and two adjacent effective vectors and a zero vector V are adopted in each sector₇To synthesize the desired voltage vector.

Compared with the prior art, the invention has the following effects:

(1) Compared with the existing common mode voltage suppression strategy, the input and output current quality is good, and the common mode voltage on the load side is further suppressed to 0.371 times of the traditional modulation strategy in a voltage transmission ratio range from 0-0.5;

(2) the rectification stage can realize zero current conversion, the current conversion control is simple, and the system reliability is improved;

Drawings

FIG. 1: a new topology of a two-stage matrix converter;

FIG. 2: the common-mode voltage generation schematic diagram of the two-stage matrix converter;

FIG. 3: (a) distributing space vector sectors in a rectification stage; (b) distribution of inverse spatial vector sectors;

FIG. 4: (a) rectifier stage I₁Direct-current side switch tube turn-off and inversion level zero vector V₀When in useA system equivalent circuit diagram; (b) rectifier stage I₁direct-current side switch tube turn-off and inversion level zero vector V₇an equivalent circuit diagram of the system in action;

FIG. 5: the coordination control chart of a rectifier stage, a direct current side and an inverter stage switching tube;

FIG. 6: (a) vector synthesis of expected input current of a rectification stage; (b) vector synthesis of expected output voltage of an inverter stage;

Detailed Description

The invention is further described below with reference to the accompanying drawings;

According to the novel topology of the two-stage matrix converter, as shown in fig. 1, a main circuit topology is composed of a rectification stage, a direct current side and an inverter stage. Wherein, the three-phase input of the rectifier stage is represented by a, b and c, the rectifier stage is a three-phase bridge circuit formed by combining six bidirectional switch units, each bidirectional switch is formed by connecting two IGBTs of a common-emitter stage in series, and the six bidirectional switch units are S_ijAnd (i ═ a, b, c; j ═ P, N) means that the input i phase is connected with the j end of the direct current bus. The DC upper and lower buses are respectively connected in series with a unidirectional switch tube, the emitter of the switch tube of the upper bus is connected with an inverter stage, the emitter of the switch tube of the lower bus is connected with a rectifier stage, and S is used respectively_PP＇、S_NN＇It means to connect the front end P and the back end P 'of the DC upper bus and the front end N and the back end N' of the DC lower bus. The three-phase output of the inverter stage is represented by A, B, C, the inverter stage is a three-phase bridge circuit formed by combining six unidirectional switching tubes, and the six unidirectional switching tubes are S_okAnd (o, A, B, C; k, P ', N') means that the output terminal o is connected with the terminal k of the direct current bus.

When a two-stage matrix converter drives a three-phase ac motor, as shown in fig. 2, the common mode voltage v_ngIs the voltage between the three-phase load neutral point n and the power supply ground point g. When the sum of the three-phase output currents is zero, the common-mode voltage satisfies the following formula:

In the formula v_Ag、v_Bg、v_CgThree-phase output phase voltages respectively;

FIG. 3 is a space vector sector distribution of the rectification stage and the inversion stage, I in FIG. 3(a)₁-I₉Representing the switching state (I) of the rectifier stage₆For example, a indicates that the upper arm of the a phase is conducted, b indicates that the lower arm of the b phase is conducted, and the rest of the switching tubes are not conducted), and V in fig. 3(b)₀-V₇Representing the switching state of the inverter stage (0 indicating the lower arm is on and 1 indicating the upper arm is on). The different switch state combinations of the rectifier stage and the inverter stage produce different common mode voltages, if the switch state of the rectifier stage is I₆The inverter stage switch state is V₀When, v_Ag＝v_Bg＝v_Cg＝v_b，v_ng＝v_btherefore, the existence of the inverse transformation level zero vector under the traditional double space vector modulation strategy, and the common mode voltage peak value is equal to the input voltage peak value V_im。

The solution of the invention is that when the inverter stage zero vector acts, the direct current side switch tube is turned off, at the moment, the direct current side current is zero, which is equivalent to a load side open circuit for the rectifier stage, and the rectifier stage can avoid using a four-step current conversion strategy to directly implement current conversion; meanwhile, due to the existence of the junction capacitance of the switching tube, the switching tube S_PP＇、S_NN＇During the turn-off period, the voltage division function is realized, and the output is prevented from being directly connected with the input. Such as when rectifying stage effective vector I₁Action, direct current side switch tube turn-off and inversion level zero vector V₀When the system is in operation, the equivalent circuit diagram of the system is shown in fig. 4(a), and the load-side common-mode voltage is expressed by equation (2); inverter level zero vector V₇In operation, the equivalent circuit diagram of the system is shown in fig. 4(b), and the load-side common mode voltage is expressed by equation (3).

In the same way, the inverter stage is zero when the DC side switch tube is disconnected in different sectors of the rectifier stageThe load side common mode voltage peaks during vectoring are shown in table 1. The load-side common-mode voltage peak value during the active vector action period of the inverter stage when the dc switch tube is turned on is the same as that of the conventional two-stage matrix converter, as shown in table 2. When the sectors of the rectifying stage are odd, the inverter stage adopts V₁V₃ V₅and V₀As effective vector and zero vector to participate in vector synthesis, when the sector of the rectifier stage is even number, the inverter stage adopts V₂ V₄V₆And V₇The amplitude of the common mode voltage peak value at the load side can be reduced to 0.371V as the effective vector and the zero vector participate in vector synthesis_im。

TABLE 1 zero vector corresponds to common mode voltage

TABLE 2 effective vector versus common mode voltage

According to the common mode voltage suppression strategy, the inverter stage adopts a seven-segment space vector modulation strategy, and when the inverter stage is in a zero vector action period, a direct current side switching tube is switched off; and during the action period of the effective vector of the inverter stage, the direct-current side switching tube is conducted, and the space vector combination of the inverter stage is divided into two types according to the parity of the sector of the rectifier stage. When the sectors of the rectifying stage are odd, the inverter stage adopts V₁ V₃ V₅And V₀As effective vector and zero vector to participate in vector synthesis, when the sector of the rectifier stage is even number, the inverter stage adopts V₂ V₅ V₆And V₇As shown in fig. 5, the method specifically includes the following steps: (the following examples are intended to be illustrative of the invention only and are not to be construed as limiting the invention)

(1) obtaining sectors N of a rectification stage and an inversion stage according to a double space vector modulation algorithm_c、N_vAnd corresponding sector angle theta_c、θ_vDetermining the modulation ratio m of the inverter stage_vSwitching period T_s；

(2) Calculating the action time of the vector, taking the example that the input current vector of the rectifier stage is positioned in a first sector and the output voltage vector of the inverter stage is positioned in a second sector as an example, describing the common mode voltage suppression strategy in detail, expecting that the input current vector passes through two adjacent effective current vectors (I)₆、I₁) The resultant effective current vector action duty ratio is d_a、d_bAs shown in FIG. 6(a), the desired output voltage vector passes through two adjacent effective voltage vectors (V)₁、V₃) And zero vector V₀The resultant effective voltage vector and zero vector duty cycles are d_m、d_n、d₀As shown in fig. 6(b), the calculation formula is as shown in formula (3);

(3) The carrier being a triangular carrier u_triAmplitude of [0,1 ]]With a period of T_s(ii) a According to the coordination of the rectifier stage, the direct-current bus and the inverter stage switching tube, as shown in fig. 5, the calculated vector action time in the step (3) is compared with the triangular carrier to generate a gate drive signal, so as to control the on and off of the rectifier stage, the direct-current bus and the inverter stage switching tube:

A rectification stage: the rectifier-stage a-phase upper bridge arm switching tube is conducted in the whole switching period, and the pulse PWM thereof_aPis always 1; when u is_tri<d_aWhen the switching tube of the b-phase lower bridge arm of the rectifier stage is switched on, the switching tube of the c-phase lower bridge arm is switched off, and pulse PWM_bNIs 1, PWM_cNIs 0; when u is_tri>d_aWhen the switching tube of the b-phase lower bridge arm of the rectifier stage is turned off, the switching tube of the c-phase lower bridge arm is turned on, and pulse PWM_bNIs 0, PWM_cN1, the pulse of the other switching tubes is constantly 0;

And D, direct current bus: when the inverter stage has zero vector action, two switching tubes S on the direct current bus are simultaneously turned off_PP＇、S_NN＇when the inverter stageDuring active vector action, S is simultaneously conducted_PP＇、S_NN' i i.e. d_a(1-d_m-d_n)/2<u_tri<d_a(1+d_m+d_n) /2 or (d)_a+d_b(1-d_m-d_n)/2)<u_tri<(d_a+d_b(1+d_m+d_n) At/2), S_PP＇、S_NN＇All are on, its pulse PWM_PP＇、PWM_NN' 1, rest of the switching cycle, S_PP＇、S_NN＇All turn off, pulse PWM thereof_PP＇、PWM_NN＇Is 0;

An inverter stage: using seven-segment space vector modulation when d_a(1-d_m-d_n)/2<u_tri<d_a(1+d_m-d_n) /2 or (1-d)_b(1+d_m-d_n)/2)<u_tri<(1-d_b(1-d_m-d_n) During/2), the A phase upper bridge arm is conducted, PWM_BpIs 1 when d_a(1+d_m-d_n)/2<u_tri<d_a(1+d_m+d_n) /2 or (1-d)_b(1+d_m+d_n)/2)<u_tri<(1-d_b(1+d_m-d_n) During/2), the B-phase upper bridge arm is conducted, PWM_Bp1, the upper bridge arm of the inverter stage C phase is switched off in the whole switching period, and pulse PWM is triggered_CpIs 0; ABC three-phase lower bridge arm trigger pulse PWM_An、PWM_Bn、PWM_CnRespectively connected with the upper bridge arm trigger pulse PWM_Ap、PWM_Bp、PWM_CpAnd (4) complementation.