CN113114032B - SVPWM common-mode voltage suppression method based on synthetic mode change - Google Patents

SVPWM common-mode voltage suppression method based on synthetic mode change Download PDF

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CN113114032B
CN113114032B CN202110464841.8A CN202110464841A CN113114032B CN 113114032 B CN113114032 B CN 113114032B CN 202110464841 A CN202110464841 A CN 202110464841A CN 113114032 B CN113114032 B CN 113114032B
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sector
given
time
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CN113114032A (en
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谭博
代佳伟
陈超波
倪志浩
蒲瑞强
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Xian Technological University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • H02M7/53875—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with analogue control of three-phase output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
    • H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention provides a method for restraining a common-mode voltage based on SVPWM under the change of a synthesis mode, which solves the problem that the common-mode voltage cannot be restrained at high and low frequencies simultaneously. The implementation comprises the following steps: establishing a topological structure of a voltage type three-level inverter; drawing a topological voltage vector diagram; decomposing four vectors of the modulation area, and changing the conduction sequence to obtain the switching time of the modulation area; performing overmodulation region three-vector decomposition to obtain overmodulation region switching time; common mode voltage rejection is accomplished. The invention carries out different common mode suppression on the modulation region and the over-modulation region, redistributes the action time in the modulation region, and suppresses the common mode voltage under high and low frequencies. The original topological structure is not changed; common mode voltage is inhibited under high and low frequencies; the switching losses are reduced. The invention has the advantages that the common-mode voltage of any voltage source PWM frequency converter driving system exists, the special environment is not needed, the high-frequency and low-frequency common-mode voltages can be inhibited, and the invention can be widely applied to the fields of automotive electronics, medical instruments and aerospace.

Description

SVPWM common mode voltage suppression method based on synthetic mode change
Technical Field
The invention belongs to the technical field of power electronics, mainly relates to suppression of common-mode voltage of a driver, and particularly relates to a SVPWM (space vector pulse width modulation) common-mode voltage suppression method based on synthetic mode change, which is widely applied to the fields of automotive electronics, medical instruments and aerospace.
Background
In recent years, voltage-type inverters have been widely used in the fields of photovoltaic power generation technology, wind power generation technology, energy storage technology, motor drive technology, and the like. The voltage-type inverter refers to an inverter in which a dc-side power source of an inverter circuit is a voltage source. The DC side of the power supply is a voltage source or is connected with a large capacitor in parallel, which is equivalent to the voltage source. The voltage at the direct current side is basically free of pulsation, and a direct current loop presents low impedance. The voltage type inverter circuit is mainly applied to various direct current power supplies and is characterized in that a direct current side is a voltage source or a large capacitor connected in parallel, and the voltage of the direct current side basically has no pulsation; the output voltage is rectangular wave, and the output current is different due to different load impedances; in order to provide a channel for the reactive power fed back from the alternating current side to the direct current side, each bridge arm of the inverter bridge is connected with a feedback diode in parallel.
The common mode voltage can induce high amplitude shaft voltage on a motor rotating shaft to form bearing current, so that a bearing of the motor is damaged in a short period, and the service life of the motor is shortened. Harmonic voltage drop can be formed on line impedance, active and reactive loss is generated, the power quality of a power supply grid is affected, and the normal operation of other electronic equipment is also affected.
The improved virtual space vector modulation method effectively suppresses the common-mode voltage by reasonably selecting the virtual medium vector distribution coefficient, but the calculation is more complex. The active common-mode voltage filter can suppress common-mode voltage, but the system has high cost, high initial investment, low operation efficiency and large volume, and is difficult to be practically applied. The VSI common-mode voltage suppression method based on voltage vector preselection only adopts a voltage vector which generates a small common-mode voltage to carry out objective function optimization and VSI control, and the influence of a dead zone is not considered, so that the common-mode voltage actually output by the VSI still contains more voltage spikes.
The elimination of the common-mode voltage by adding the feedforward active filter, which is proposed by Jiang Yanshu of the harbin industry university, can inhibit the generation of the common-mode voltage, but the structure is complex, additional equipment needs to be added, and the cost and the complexity of the system are increased; the southwest traffic university is responsible for synthesizing a virtual voltage vector of zero harmonic plane voltage by using only a small vector and a large vector of low common-mode voltage to control a five-phase PMSM, and the suppression of the common-mode voltage is realized without adding a new control target in a cost function, but the change frequency of the common-mode voltage is too high, and the switching loss is large; wang Lina of the university of the middle and south selects only 6 voltage vectors with the common-mode voltage of 0 to control the motor, so that the common-mode voltage in a matrix converter driving PMSM system is eliminated, but the torque ripple of the PMSM is obviously increased, and the steady-state characteristic of the system is reduced.
The prior art eliminates common mode voltage mostly by changing topology and adding feedforward active filter, and by changing modulation strategy, but these methods will generate more switching loss, may add extra equipment, and increase cost and complexity.
Disclosure of Invention
In order to inhibit the common-mode voltage, the invention provides the SVPWM common-mode voltage inhibiting method based on the change of the synthesis mode, which has the advantages of small switching loss, good isolation effect and high efficiency.
The invention relates to a SVPWM common-mode voltage suppression method based on synthesis mode change, which is characterized by comprising the following steps of:
step 1: establishing the topology of the driver: the topological structure is derived from a voltage type three-phase inverter, the driver is connected with three bridge arms A, B, C in parallel according to the sequence from an input end to an output end, and the bridge arms are mutually connected in parallel between 1/2U and-1/2U circuit ends according to A, B, C; each bridge arm comprises a MOSFET N-type switch tube, a diode, a resistor and an inductor, a switch unit is formed by connecting the MOSFET N-type switch tube and the diode in parallel, the two switch units are connected on each bridge arm in series, and the inductor L is sequentially connected between the two switch units of the driver bridge arm A in series a And a resistor R a (ii) a An inductor L is connected in series between two switch units of a driver bridge arm B in sequence b Resistance R b (ii) a An inductor L is connected in series between two switch units of a driver bridge arm C in sequence c And a resistor R c (ii) a The resistance of each bridge arm is the same as the precision grade of the inductance, and the full-scale capacity is the same; a driver bridge arm A,B. C, the inductor and the resistor which are sequentially connected in series between the two switch units are connected to a circuit node O together, and the node is the output end of the driver; bridge arms which form a topological structure of the voltage type three-phase inverter as a whole are mutually connected in parallel between 1/2U and-1/2U circuit ends according to the sequence of A, B, C;
step 2: drawing a topological voltage vector diagram of the driver: according to the topological structure of the voltage type three-phase inverter established in the step 1, defining the switch units on three bridge arms of the driver: the switching unit between 1/2U voltage ends of the A bridge arm is 1, the switching unit between-1/2U circuit ends of the C bridge arm is 2, the switching unit between 1/2U voltage ends of the B bridge arm is 3, the switching unit between-1/2U voltage ends of the A bridge arm is 4, the switching unit between 1/2U voltage ends of the C bridge arm is 5, and the switching unit between-1/2U voltage ends of the B bridge arm is 6; the switching state of each switching unit is represented by 1 or 0; each driver has eight states, after the states of 000 and 111 are removed by international regulations, the other six states form six different sectors, the angle of each sector is 60 degrees, wherein the vector in the positive horizontal direction is 100, the rotation is performed in the counterclockwise direction, the 60 degrees are taken as intervals, the other vectors are 110, 010, 011, 001 and 101 in sequence, six sectors with 60 degrees are formed, a first sector is formed between the vectors 100 and 110, a second sector is formed between the vectors 110 and 010, and the rest sectors are analogized in the counterclockwise direction;
and step 3: and (3) adopting four-vector synthesis of voltage in the modulation interval, and adjusting the conduction sequence of the switch units to obtain the switching time in the modulation interval: decomposing the given voltage in each sector according to a topological voltage vector diagram of six sectors of the driver to obtain four action times of the given voltage of different sectors; assuming a given voltage is in the first sector, the duration of the given voltage acting on vector 100 is set to x 1 Setting the application time of a given voltage on vector 110 to x 2 Setting the application time of a given voltage on vector 010 to x 3 Setting the application time of a given voltage on vector 101 to x 4 Then the related vectors of the given voltage in the first sector and the second sector participate in the decomposition to obtain the voltage vector U under the two-phase static coordinate system alpha beta α1 、U β1 (ii) a The voltage vector is used as the input of the modulation wave calculation module, the conduction sequence of the switch units is adjusted, the related vectors of the first sector and the second sector are redistributed, and the action time x on the vector 100 is changed 1 Redefining the action time as 010 vector action time x 3 Redefined as action time on 100 vectors, action time x on vector 110 2 Time of action x on sum vector 101 4 Keeping the original shape; observing a waveform diagram in a first sector modulation interval of the voltage type three-phase inverter, and modulating to obtain the switching time a of a drive topological structure 1 ＝x 2 +x 3 +x 4 a 2 ＝x 1 +x 2 a 3 ＝x 4 (ii) a And analogizing in turn, each sector has the same calculation, and the switching time a of four voltage vectors obtained after each sector in the modulation interval decomposes the given voltage of the driver is obtained 1 、a 2 、a 3 ；
And 4, step 4: and (3) performing voltage three-vector synthesis on the overmodulation region to obtain the switching time outside the interval: decomposing the given voltage in each sector according to a topological voltage vector diagram of six sectors of the driver to obtain three action times of the given voltage of different sectors; arranging all the obtained action time in sequence, and setting the action time of the given voltage on the vector 100 to be x on the assumption that the given voltage is in the first sector 1 Setting the application time of a given voltage on vector 110 to x 2 Setting the application time of a given voltage on vector 010 to x 3 Then the related vectors of the given voltage in the first sector and the second sector participate in the decomposition to obtain the voltage vector U under the two-phase static coordinate system alpha beta α 、U β (ii) a The voltage vector is used as the input of a modulation wave calculation module to generate a waveform, the first sector and the related vectors of the second sector are arranged according to the action time sequence, the waveform diagram of the overmodulation region of the first sector of the voltage type three-phase inverter is observed and modulated to obtain the switching time a of the topological structure of the voltage type three-phase inverter 1 ＝x 2 +x 3 、a 2 ＝x 1 +x 2 、a 3 =0; and analogizing in turn, each sector has the same calculation, and the switching time a of three voltage vectors after each sector of the overmodulation region decomposes the given voltage of the drive is obtained 1 、a 2 、a 3 ；
And 5: finishing SVPWM restraining common mode voltage based on change in synthesis mode: and according to a switching time oscillogram drawn by redistribution of the six sector areas, the switching time of a modulation area and the switching time of an overmodulation area are modulated through experiments, and the suppression of the common-mode voltage of the voltage type three-phase inverter is realized.
The invention can inhibit the common-mode voltage under high and low frequencies simultaneously by changing the modulation strategy without adding extra devices and equipment or increasing cost and complexity, and solves the technical problem of inhibiting the common-mode voltage of the voltage type three-phase inverter under the high and low frequencies.
Compared with the prior art, the invention has the technical advantages that:
the topological structure is simple, and the building and understanding are convenient: the topological structure for inhibiting the common-mode voltage is simple, the topological structure consists of three-phase bridge arms, each phase of bridge arm is provided with an MOSFET N-type switch tube, a diode, a resistor and an inductor, the MOSFET N-type switch tube and the diode are connected in parallel to form a switch unit, each bridge arm is provided with two switch units which are connected in series, and other devices are respectively connected with the switch units in parallel. The device is simple and clear, convenient to build and understand, convenient to engineer and apply and realize, and the overall complexity is reduced.
Common mode voltage can be restrained under high and low frequencies: the method comprises the steps of inhibiting the common-mode voltage of a modulation area and inhibiting the common-mode voltage of an overmodulation area, firstly decomposing four vectors of a given voltage for each sector in a modulation interval to obtain the action time of each sector, changing the conduction sequence of a switching unit of an inverter, combining the voltage vectors of the given voltage which is obtained in each sector through change in a two-phase static coordinate system with a carrier, drawing a waveform diagram, and obtaining the switching time of each sector. And secondly, decomposing three vectors of the given voltage in an overmodulation region for each sector to obtain the action time of each sector, arranging the action time in sequence, combining a voltage vector obtained by changing the given voltage in each sector under a two-phase static coordinate system with a carrier, drawing a waveform diagram, and obtaining the switching time of each sector. Through calculation and experiments, the common-mode voltage can be inhibited at high and low frequencies.
Switching losses can be reduced: the modulation method in the overmodulation region is characterized in that three action times are arranged in sequence, a voltage vector obtained by changing a given voltage in each sector under a two-phase static coordinate system is combined with a carrier, a waveform diagram is drawn, and the switching time of each sector is obtained. According to the waveform diagram, each sector has a switching time of 1 or 0, and the driver has a switching device in a normally-on or normally-off state. Through calculation and experiments, it is found that the switching loss can be reduced.
Drawings
FIG. 1 is a block flow diagram of the present invention;
FIG. 2 is a circuit block diagram of a voltage source three phase inverter;
FIG. 3 is a distribution diagram of a first sector;
FIG. 4 is a modulation waveform for a first sector within a maximum voltage utilization interval;
FIG. 5 is a modulation waveform for a first sector outside of a maximum voltage utilization interval;
FIG. 6 is a schematic diagram of the maximum voltage utilization ranges obtained by different modulation methods of the driver;
fig. 7 is a graph of common mode voltage experiment according to the present invention, in which fig. 7 (a) is a graph of common mode voltage of third harmonic injection, fig. 7 (b) is a graph of common mode voltage of conventional SVPWM, and fig. 7 (c) is a graph of common mode voltage according to the present invention.
Detailed Description
Example 1
There are many studies on common mode voltage rejection, but the study time is short, so the technology is not perfect, and there are many that can be continued to study and learn. The invention provides an innovative modulation technology based on the prior art.
The invention relates to a method for restraining common-mode voltage based on SVPWM under the change of a synthesis mode, which is shown in figure 1 and comprises the following steps:
step 1: establishing a topological structure of the voltage type three-phase inverter: the topological structure is originated from a driver, the driver is connected with three bridge arms A, B, C in parallel according to the sequence from an input end to an output end, and the bridge arms are mutually connected in parallel between 1/2U circuit ends and-1/2U circuit ends according to the sequence A, B, C. Each bridge arm comprises an MOSFET N-type switching tube, a diode, an inductor and a resistor, referring to fig. 2, the diode mainly serves to store current, the rated current is assumed to be 10A, the current of the diode is the rated current multiplied by 1.5+ a certain allowance, and therefore the diode with the current of about 20A is selected; the MOSFET N-type switch tube also selects the switch tube with the current magnitude of about 20A. The invention relates to a switch unit formed by connecting MOSFET N-type switch tubes and diodes in parallel, wherein two switch units are connected in series on each bridge arm, and an inductor L is sequentially connected in series between the two switch units of the driver bridge arm A a Resistance R a (ii) a Inductors L are sequentially connected between two switch units of the driver bridge arm B in series b And a resistor R b (ii) a Inductors L are sequentially connected between two switch units of the driver bridge arm C in series c Resistance R c . The resistance of each bridge arm is the same as the inductance precision grade, and the full-scale capacity is the same.
According to the invention, resistors and inductors are sequentially connected in series between two switch units of a driver bridge arm A, B, C and are commonly connected to a circuit node O, referring to fig. 2, the bridge arms which form the topological structure of the voltage type three-phase inverter as a whole are mutually connected in parallel between 1/2U and-1/2U circuit ends according to the A, B, C sequence; the topology structure diagram for restraining the common-mode voltage based on the SVPWM under the change of the synthesis mode is generally formed.
And 2, step: drawing a topological voltage vector diagram of the driver: according to the topological structure of the common-mode voltage of the driver, the three bridge arms of the driver are provided with switch units formed by connecting MOSFET N-type switch tubes and diodes in parallel, the switch unit between the 1/2U voltage ends of the A bridge arm is defined as 1, the switch unit between the-1/2U circuit ends of the C bridge arm is defined as 2, the switch unit between the 1/2U voltage ends of the B bridge arm is defined as 3, the switch unit between the-1/2U voltage ends of the A bridge arm is defined as 4, the switch unit between the 1/2U voltage ends of the C bridge arm is defined as 5, and the switch unit between the-1/2U voltage ends of the B bridge arm is defined as 6, as shown in figure 2. The switching state of each switching unit is represented by 1 or 0, the switching unit conduction between the voltage ends of 1/2U of A, B, C three-phase bridge arm is represented by 1, the switching unit conduction between the voltage ends of 0,A and B, C three-phase bridge arm-1/2U is represented by 0, the switching unit conduction between the voltage ends of 1/2U is represented by 1, eight states are formed totally, after removing 000 and 111 states, the rest states of 100, 110, 010, 011, 001 and 101 form six different sectors, the angle of each sector is 60 degrees, the vector in the positive horizontal direction is represented by 100, the rotation is performed in the counterclockwise direction at 60 degrees, the rest vectors are sequentially 110, 010, 011, 001 and 101, six sectors with 60 degrees are formed, and the distribution diagram of the first sector is shown in fig. 3. The first sector is between vectors 100 and 110, the second sector is between vectors 110 and 010, and so on.
And step 3: and adopting four-vector synthesis of voltage in the modulation interval, and adjusting the conduction sequence of the switch units to obtain the switching time in the modulation interval: according to the invention, the common-mode voltage can be increased by injecting the zero vector according to the accumulated experience of long-term operation. In the voltage type three-phase inverter, a third harmonic injection modulation method is a red inner circle, see fig. 6, and the area of the red inner circle is called as a modulation area. Decomposing the given voltage in each sector according to a topological voltage vector diagram of six sectors of the driver to obtain four action times of the given voltage of different sectors; assuming a given voltage is in the first sector, see FIG. 3, the duration of the given voltage on vector 100 is set to x 1 Setting the application time of a given voltage on vector 110 to x 2 Setting the application time of a given voltage on vector 010 to x 3 Setting the application time of a given voltage on vector 101 to x 4 Then the related vectors of the given voltage in the first sector and the second sector participate in the decomposition to obtain the voltage vector U under the two-phase static coordinate system alpha beta α1 、U β1 Completing the four-vector synthesis of the voltage for the modulation interval. The voltage vector is used as the input of the modulation wave calculation module, the conduction sequence of the switch units is adjusted, the first sector and the relevant vector of the second sector are redistributed, and the action time x of the vector 100 is determined by assuming that the given voltage is in the first sector 1 Redefining the action time as 010 vector action time x 3 Redefined as action time on 100 vectors, action time x on vector 110 2 Time of action x on sum vector 101 4 Keeping the same; observing a waveform diagram in a modulation interval of a first sector of the voltage type three-phase inverter, and referring to fig. 4, wherein fig. 4 is a modulation waveform of the first sector in the modulation interval to obtain a switching time a of a drive topological structure 1 ＝x 2 +x 3 +x 4 a 2 ＝x 1 +x 2 a 3 ＝x 4 (ii) a And analogizing in turn, each sector has the same calculation, and the switching time a of four voltage vectors obtained after each sector in the modulation interval decomposes the given voltage of the driver is obtained 1 、a 2 、a 3 ；
And 4, step 4: and (3) performing voltage three-vector synthesis on the overmodulation region to obtain the switching time of a section: in a voltage type three-phase inverter, a traditional SVPWM modulation technology is a green excircle, see FIG. 6, the invention provides a new modulation technology, namely a blue regular hexagon, and a sector area between the blue regular hexagon and the green excircle is called an overmodulation area. Decomposing the given voltage in each sector according to a topological voltage vector diagram of six sectors of the driver to obtain three action times of the given voltage of different sectors; all the application times are arranged in sequence, and assuming that a given voltage is in the first sector, see fig. 3, the application time of the given voltage on the vector 100 is set to x 1 Setting the application time of a given voltage on vector 110 to x 2 Setting the application time of a given voltage on vector 010 to x 3 Then the relevant vectors of the given voltage in the first sector and the second sector participate in the decomposition to obtain the voltage vector U under the two-phase static coordinate system alpha beta α 、U β (ii) a Voltage vector as a toneAnd generating a waveform by the input of the wave modulation calculation module, arranging the first sector and the related vectors of the second sector according to the action time sequence, observing a waveform diagram of an overmodulation region of the first sector of the voltage type three-phase inverter, and modulating, wherein the waveform diagram is observed, and fig. 5 is a modulated waveform of the first sector of the overmodulation region. Obtaining the switching time a of the driver topology 1 ＝x 2 +x 3 、a 2 ＝x 1 +x 2 、a 3 =0; and analogizing in turn, each sector has the same calculation to obtain the switching time a of the SVPWM based on the change of the synthesis mode 1 、a 2 、a 3 。
And 5: finishing SVPWM restraining common mode voltage based on change in synthesis mode: and modulating the switching time of the modulation region and the overmodulation region according to a switching time oscillogram drawn by redistribution of the six fan-shaped regions, and simulating to realize the suppression of the common-mode voltage.
The problems of the prior art: the "space vector modulation technique" will increase the harmonics of the power converter output voltage; the space vector modulation method with synchronously changed switches on the current side and the inversion side does not really eliminate common-mode voltage, but only plays a role in limiting common-mode current on the motor side; the chopping strategy of the isolating transformer is adopted, so that common-mode voltage is not completely eliminated, and the method has the defects of high energy consumption, low efficiency, low power factor, high starting impact, poor isolation effect and the like.
The idea of the invention is as follows: on the basis of the prior art, the invention provides a topological structure of the voltage type three-level inverter aiming at the problems, calculates the switching time of a modulation region and the switching time of an overmodulation region, and realizes the suppression of high-frequency and low-frequency common mode voltage.
The technical means of the invention are as follows: the invention provides a complete technical scheme for inhibiting high-low frequency common-mode voltage, provides a topological structure of a voltage type three-level inverter, carries out four-vector decomposition on given voltage in a modulation region to obtain action time of different sectors, combines the decomposed voltage vectors with a carrier wave to be used as the input of a modulation wave calculation module, and combines the 6 switching units of the prior voltage type three-level inverterThe turn-on sequence is changed, see fig. 2, taking sector i as an example, the original action time x 1 The corresponding sequence is that the switch unit 1, the switch unit 6 and the switch unit 2 are conducted, namely the state 100, the switch unit 4, the switch unit 3 and the switch unit 2 are conducted instead, namely the state 010, and the original action time x 3 The corresponding sequence is that the switch unit 4, the switch unit 3 and the switch unit 2 are conducted, namely, the state 010 is changed into the state that the switch unit 1, the switch unit 6 and the switch unit 2 are conducted, namely, the state 100, other states are unchanged, other sectors are analogized in sequence, a waveform diagram is drawn, and the switching time of the power device is obtained. And then three-vector decomposition is carried out on the given voltage in the overmodulation region to obtain the action time of different sectors, the decomposed voltage vector is combined with a carrier wave to be used as the input of a modulation wave calculation module, and a waveform diagram is drawn to obtain the switching time of the power device. Experiments are completed, and the invention is verified to be capable of inhibiting high and low frequency common mode voltage.
The invention has the technical effects that: the invention provides a method for suppressing common-mode voltage based on SVPWM under synthesis mode change, which not only redistributes the action time of a modulation region, but also combines the common-mode voltage suppression schemes of the modulation region and an overmodulation region, further improves the original method for suppressing the common-mode voltage, reduces the switching loss, keeps the voltage utilization rate unchanged, suppresses the common-mode voltage under high and low frequencies, and reduces the damage to a motor and other devices.
In the prior art, the classic chopping strategy of 'adopting an isolation transformer' for common-mode voltage can be eliminated, and the common-mode voltage can be inhibited, but the defects of high energy consumption, low efficiency, low power factor, high starting impact, poor isolation effect and the like are overcome. The invention aims at the problem that common mode voltage of a general voltage type three-level inverter is difficult to inhibit at high and low frequencies, a topological structure is constructed for the three-level inverter, a voltage vector model is formed for a single driver, the interrelation among six sectors is provided on the basis of the vector model, the fixed voltage can be assigned to be decomposed into four action times in each sector of a modulation area, the action times are redistributed, a waveform diagram is drawn to be modulated to obtain switching time, then the fixed voltage is assigned to be decomposed into three action times in each sector of an overmodulation area, the action times are sequentially assigned, the waveform diagram is drawn to be modulated to obtain the switching time, experimental verification is carried out, and the high and low frequency common mode voltage is successfully inhibited.
Example 2
The method for suppressing the common mode voltage based on the SVPWM under the change of the synthesis mode is the same as the method in the embodiment 1 and the step 3, as shown in fig. 6, a red inner circle is a modulation technology of third harmonic injection, and a red inner circle area corresponds to a modulation area, the blue regular hexagon tangent to the inner circle provided by the invention can increase a maximum voltage utilization rate interval, the modulation area adopts the voltage four-vector synthesis to obtain the action time of the modulation area, the action time is rearranged, a waveform diagram is drawn, the obtained linear relation between a given voltage vector and the action time is substituted into the switching time to obtain a mathematical expression of the given voltage vector and the switching time, and the switching time of the modulation area is obtained, taking the first sector voltage as an example, the method comprises the following steps:
(3.1) given the voltage vector decomposition expression: the first sector voltage vector decomposition expression is:
Figure BDA0003042960780000101
wherein:
Figure BDA0003042960780000102
setting a voltage for the driver; x is a radical of a fluorine atom 1 、x 2 、x 3 、x 4 Four action times for a given voltage after the first sector decomposition, wherein the action time of the given voltage on the vector 010 is x 1 Setting the application time of a given voltage on vector 110 to x 2 Setting the application time of a given voltage on vector 100 to x 3 Setting the application time of a given voltage on vector 101 to x 4 ；
Figure BDA0003042960780000103
Figure BDA0003042960780000104
Is a sector voltage vector corresponding to the resolution of the given drive voltage in the first sector and two sectors adjacent to the first sector;
(3.2) setting limiting conditions: the first sector voltage vector calculation constraints are:
Figure BDA0003042960780000105
in the formula, x 1 、x 2 、x 3 、x 4 Four action times after the decomposition of the given voltage in the first sector are given;
(3.3) calculating a voltage vector: performing module value calculation on the given voltage in the first sector to obtain module value
Figure BDA0003042960780000106
Substituting the transformation angle to calculate a voltage vector under the two-phase static coordinate system alpha beta: u shape α1 、U β1
Figure BDA0003042960780000107
In the formula of U α1 For a component, U, in a two-phase stationary coordinate system alpha after a given voltage decomposition β1 The component under a two-phase static coordinate system beta after the given voltage decomposition is taken as the component;
(3.4) obtaining the action time of the given voltage of the first sector: substituting the limiting conditions into a given voltage vector decomposition expression of the first sector to obtain the action time of the first sector:
Figure BDA0003042960780000111
in the formula, x 1 For a given duration of application of voltage to vector 010, x 2 For a given voltage applied to vector 110 for an applied time, x 3 To be set toThe duration of action of a constant voltage on vector 100, x 4 To set the application time of a given voltage on vector 101,
Figure BDA0003042960780000112
is the standard vector length.
(3.5) redistribution of the conduction order of the switching cells: the action time x on the vector 100 1 Redefined as the time of action on the 010 vector, x on the 010 vector 3 Redefined as action time on 100 vectors, action time x on vector 110 2 Time of action x on sum vector 101 4 Remain unchanged. The action time x of redistribution after decomposing the obtained given voltage vector of the first sector driver 1 、x 2 、x 3 、x 4 Combining with carrier waves, drawing a waveform chart to obtain switching time a based on a single driver topological structure 1 、a 2 、a 3 And analyzing the oscillogram to obtain:
a 1 ＝x 2 +x 3 +x 4 a 2 ＝x 1 +x 2 a 3 ＝x 4
in the formula, a 1 、a 2 、a 3 Switching time, x, based on voltage-type three-phase inverter topology 1 、x 2 、x 3 、x 4 Four action times after the decomposition of the given voltage in the first sector are given;
(3.6) obtaining a relation between the switching time and a given voltage vector: combining the relation between the switching time and the action time of the first sector and the relation between the given voltage vector and the action time to obtain a relation:
Figure BDA0003042960780000113
in the formula, a 1 、a 2 、a 3 For switching time based on single driver topology, U α1 、U β1 The given voltage of the driver is resolved under a two-phase static coordinate system alpha betaThe vector of the result is then calculated,
Figure BDA0003042960780000121
and (4) obtaining the switching time of the modulation area of the first sector for the standard vector length, and returning to the step (3.1) for calculating the switching time of the next sector.
(3.7) obtaining the switching time of the given voltage of all sectors: and (3.1) to (3.6) are executed in a circulating way, other sectors are sequentially executed according to the same method, the relational expression of the switching time of all sectors in the modulation area and the given voltage vector is calculated, and the switching time a of four voltage vectors after each sector in the modulation area is decomposed to the given voltage of the driver is obtained 1 、a 2 、a 3 。
The method comprises the steps of decomposing a given voltage in a modulation area to obtain four voltage vectors, changing the conduction sequence of a switching unit of an inverter, combining the voltage vectors and a carrier wave of the given voltage in each sector, wherein the voltage vectors and the carrier wave are obtained under a two-phase static coordinate system through changing the given voltage, drawing a waveform diagram, and obtaining the switching time of each sector. The suppression of low-frequency common-mode voltage is innovatively solved, no additional device or equipment is added, no excessive program is added, the complexity is low, and the calculation is simple and quick.
Example 3
The method for suppressing common-mode voltage by using SVPWM based on synthetic mode change is the same as that in embodiment 1-2 and step 4, referring to FIG. 6, the blue regular hexagon tangent to the inner circle provided by the invention can increase the maximum voltage utilization rate interval, the green outer circle tangent to the blue regular hexagon is the traditional SVPWM modulation technology, the sector interval between the outer circle and the regular hexagon is called as an overmodulation area, voltage three-vector synthesis is adopted in the overmodulation area to obtain the action time of the overmodulation area, the action time sequence is arranged, a waveform diagram is drawn, the linear relation between the obtained given voltage vector and the action time is substituted into the switching time to obtain the mathematical expression between the given voltage vector and the switching time, and the switching time of the overmodulation area is obtained, taking the first sector voltage as an example, and the method comprises the following steps:
(4.1) given the voltage vector decomposition expression: the first sector voltage vector decomposition expression is:
Figure BDA0003042960780000122
wherein:
Figure BDA0003042960780000123
setting a voltage for the driver; x is the number of 1 、x 2 、x 3 Four action times for a given voltage after the first sector decomposition, wherein the action time of the given voltage on the vector 010 is x 1 Setting the application time of a given voltage on vector 110 to x 2 Setting the application time of a given voltage on vector 100 to x 3 ；
Figure BDA0003042960780000131
Is a voltage vector of a given voltage which is decomposed in a first sector and a second sector;
(4.2) calculating a voltage vector: performing module value calculation on the given voltage in the first sector to obtain module value
Figure BDA0003042960780000132
Substituting the transformation angle to calculate a voltage vector under the two-phase static coordinate system alpha beta: u shape α 、U β
Figure BDA0003042960780000133
In the formula, x 1 、x 2 、x 3 For four action times, U, after the decomposition of the first sector for a given voltage α For a component, U, in a two-phase stationary coordinate system alpha after a given voltage decomposition β The component under a two-phase static coordinate system beta after the given voltage decomposition is taken as the component;
(4.3) limiting conditions: the first sector voltage vector calculation constraints are:
Figure BDA0003042960780000134
in the formula of U α For a given voltage resolved component, U, in a two-phase stationary coordinate system alpha β Decomposing the component of the given voltage under a two-phase static coordinate system beta;
(4.4) obtaining the action time of the given voltage of the first sector: substituting the limiting conditions into a given voltage vector decomposition expression of the first sector to obtain the action time of the first sector:
Figure BDA0003042960780000135
in the formula, x 1 For a given duration of application of voltage to vector 010, x 2 For a given voltage applied to vector 110 for an applied time, x 3 To set the application time for a given voltage to be applied to vector 100,
Figure BDA0003042960780000141
is the standard vector length.
(4.5) decomposing the obtained first sector given voltage vector to obtain action time x 1 、x 2 、x 3 Arranging according to the decomposition sequence, combining with a carrier wave, drawing a waveform diagram to obtain the switching time a based on the topological structure of a single driver 1 、a 2 、a 3 And analyzing the image to know that:
a 1 ＝x 2 +x 3 a 2 ＝x 1 +x 2 a 3 ＝0
in the formula, a 1 、a 2 、a 3 Switching time, x, based on voltage-type three-phase inverter topology 1 、x 2 、x 3 Three action times after the first sector is decomposed for the given voltage;
(4.6) combining the relation of the switching time and the action time of the first sector and the relation of the given voltage vector and the action time to obtain a relation:
Figure BDA0003042960780000142
in the formula, a 1 、a 2 、a 3 For switching time based on single driver topology, U α 、U β Returning to the step (4.1) to calculate the switching time of the next sector for the vector obtained under the two-phase static coordinate system alpha beta after the given voltage is decomposed;
(4.7) obtaining the switching time of the given voltage of all sectors: and (4.1) to (4.6) are executed in a circulating way, and other sectors are sequentially executed according to the same method, so that the switching time of the given voltage of all the sectors of the overmodulation region is obtained.
Aiming at the suppression of the high-frequency common-mode voltage of the overmodulation region, three voltage vectors obtained by decomposing a given voltage in the overmodulation region are combined with a carrier wave through the voltage vectors obtained in each sector through change in a two-phase static coordinate system, a waveform diagram is drawn, action time is sequentially arranged and modulated, the switching time of each sector of the overmodulation region is obtained, the switching loss is effectively reduced, and the efficiency is generally improved.
In the current research technology, with the continuous development of the technology and the continuous increase of the switching frequency, the solution of the common mode voltage problem is usually some engineering measures, but after the measures are implemented, only one specific problem can be solved, and no way is provided for suppressing the high and low frequency common mode voltage and reducing the switching loss. The method specifically includes the steps that voltage action time and modulation are researched for a modulation area and an overmodulation area, a simple topological structure is provided, four-vector decomposition is conducted on given voltage in each sector in the modulation area to obtain action time, the action time obtained by decomposition of the given voltage in each sector is redistributed, the given voltage is changed in each sector to obtain voltage vectors and carrier waves which are combined in a two-phase static coordinate system, a waveform diagram is drawn, and switching time of each sector in the modulation area is obtained; and performing three-vector decomposition on the given voltage in each sector in the overmodulation region to obtain action time, sequentially arranging the action time obtained by decomposing the given voltage in each sector, combining a voltage vector obtained by changing the given voltage in each sector under a two-phase static coordinate system with a carrier wave, drawing a waveform diagram, and obtaining the switching time of each sector in the overmodulation region. Through calculation and experiments, the common mode voltage capable of suppressing high and low frequencies can be obtained.
An experimental example is given below to explain the technical effects of the present invention
Example 4
The method for suppressing the common mode voltage based on the SVPWM under the variation of the synthesis mode is the same as that of examples 1 to 3,
experimental conditions and contents:
in the experiment, the rated voltage is set to be 28V, and the rated current is set to be 2A; the maximum GS voltage of the MOSFET N-type switching tube is generally-20V to 20V, the maximum working temperature is 150 ℃ to 175 ℃, and the current is about 3A; the current of the diode is about 3A.
In the experiment, a circuit board participating in the experiment is arranged, a driver is a voltage type three-phase inverter circuit, a power supply supplies power to the circuit board, and an oscilloscope probe is connected to the output end of the circuit and a corresponding modulation node.
Experimental results and analysis:
fig. 7 is a graph of common mode voltage experiment according to the present invention, in which fig. 7 (a) is a graph of common mode voltage of third harmonic injection, fig. 7 (b) is a graph of common mode voltage of conventional SVPWM, and fig. 7 (c) is a graph of common mode voltage according to the present invention.
According to the innovation provided by the invention, different modulation methods are adopted for different intervals, action time obtained by decomposing different intervals is combined with carrier waves, the oscillogram of an oscilloscope is observed, and switching time of different intervals is obtained, as shown in figure 7, and figure 7 is an experimental oscillogram of the invention; in fig. 7, the abscissa indicates frequency and the ordinate indicates amplitude, where fig. 7 (a) is a graph of common mode voltage of third harmonic injection, fig. 7 (b) is a graph of common mode voltage of conventional SVPWM, and fig. 7 (c) is a graph of common mode voltage of the present invention. The two large amplitude curves of yellow and blue in fig. 7 (a), 7 (b), and 7 (c) respectively represent two legs A, B of the voltage-type three-phase inverter circuit, see fig. 2, where the yellow and blue curves are labeled as curves 1 and 2; the purple interval is high-frequency common mode voltage and is marked as 3, and the green sine wave is low-frequency common mode voltage and is marked as 4; the red line is the subtraction operation of the bridge arm a and the low frequency common mode voltage, and is marked as 5. In fig. 7 (a), the purple interval represents the high-frequency common-mode voltage, the peak-peak value is 10.8V, the green sine wave represents the low-frequency common-mode voltage, and the amplitude value is 1.61V; in fig. 7 (b), the purple interval represents the high-frequency common-mode voltage, the peak-peak value is 30.8V, the green sine wave represents the low-frequency common-mode voltage, and the amplitude is 2.11V; according to the experimental result of the invention, referring to fig. 7 (c), the purple interval in fig. 7 (c) represents the high-frequency common-mode voltage, the peak-peak value is 10.6V, the green sine wave represents the low-frequency common-mode voltage, and the amplitude value is 716mV. Comparing fig. 7 (a), fig. 7 (b), and fig. 7 (c), it is apparent that the present invention achieves suppression of common mode voltage at high and low frequencies, and reduction of switching loss. The SVPWM common-mode voltage suppression method based on the change of the synthesis mode can successfully suppress the common-mode voltage under high and low frequencies.
In summary, the method for inhibiting the common-mode voltage based on the SVPWM under the change of the synthesis mode of the present invention solves the problem that the common-mode voltage cannot be inhibited at high and low frequencies when the common-mode voltage is eliminated by the existing method. The implementation steps are as follows: establishing a topological structure of the voltage type three-level inverter; performing four-vector decomposition on the given voltage in different sectors of the modulation area to obtain action time of different sectors of the modulation area, redistributing all the action time, and drawing a oscillogram to obtain switching time of the modulation area; performing three-vector decomposition on the given voltage in different sectors of the overmodulation region to obtain the action time of the different sectors of the overmodulation region, sequentially arranging all the action time, drawing a waveform diagram to obtain the switching time of the overmodulation region; the rejection of the common mode voltage of the three-level inverter at high and low frequencies is completed. The invention provides that different modulation methods are adopted in different intervals, so that given voltage is subjected to vector decomposition in each sector of the different intervals to obtain action time; the voltage of given voltage decomposed in a two-phase static coordinate system is used as the input of a modulation wave calculation module to generate a waveform, action time is redistributed and modulated, and common-mode voltage can be inhibited at high and low frequencies. The invention has simple topological structure, easy construction and convenient understanding; common mode voltage can be inhibited at high and low frequencies; the switching losses are reduced. In any voltage source PWM frequency converter driving system, common mode voltage exists, and although common mode components do not exist in differential mode voltage output by the inverter, common mode current generated by the common mode voltage flows through a load. The invention does not need specific environment, can inhibit common-mode voltage under high and low frequencies, and has wider application in the fields of automotive electronics, medical instruments and aerospace.

Claims (3)

1. A SVPWM common mode voltage suppression method based on synthesis mode change is characterized by comprising the following steps:
step 1: establishing the topology of the driver: the topological structure is derived from a voltage type three-phase inverter, the driver is connected with three bridge arms A, B, C in parallel according to the sequence from an input end to an output end, and the bridge arms are mutually connected in parallel between 1/2U and-1/2U circuit ends according to A, B, C; each bridge arm comprises a MOSFET N-type switch tube, a diode, a resistor and an inductor, a switch unit is formed by connecting the MOSFET N-type switch tube and the diode in parallel, the two switch units are connected on each bridge arm in series, and the inductor L is sequentially connected in series at a connection node between the two switch units of the driver bridge arm A a Resistance R a (ii) a An inductor L is sequentially connected in series at a connection node between two switch units of a bridge arm B of the driver b And a resistor R b (ii) a An inductor L is sequentially connected in series at a connection node between two switch units of a bridge arm C of the driver c Resistance R c (ii) a The precision grade of the resistance of each bridge arm is the same as that of the inductance, and the full-scale capacity is equal; the inductor and the resistor which are sequentially connected in series at the connecting node between the two switch units of the driver bridge arm A, B, C are connected to a circuit node O together, and the node O is the output end of the driver;
and 2, step: drawing a topological voltage vector diagram of the driver: according to the topological structure of the voltage type three-phase inverter, the switch units on three bridge arms of the driver are defined: the switching unit between 1/2U voltage ends of the A bridge arm is 1, the switching unit between-1/2U circuit ends of the C bridge arm is 2, the switching unit between 1/2U voltage ends of the B bridge arm is 3, the switching unit between-1/2U voltage ends of the A bridge arm is 4, the switching unit between 1/2U voltage ends of the C bridge arm is 5, and the switching unit between-1/2U voltage ends of the B bridge arm is 6; the switching state of each switching unit is represented by 1 or 0; each drive has eight states, after international regulations remove the states of 000 and 111, the other six states form six different sectors, the angle of each sector is 60 degrees, wherein the vector in the positive horizontal direction is 100, the rotation is in the counterclockwise direction, the interval is 60 degrees, the other vectors are 110, 010, 011, 001 and 101 in sequence, six sectors with 60 degrees are formed, a first sector is between the vectors 100 and 110, a second sector is between the vectors 110 and 010, and the rest sectors are analogized in the counterclockwise direction;
and step 3: and adopting four-vector synthesis of voltage in the modulation interval, and adjusting the conduction sequence of the switch units to obtain the switching time in the modulation interval: decomposing the given voltage in each sector according to a topological voltage vector diagram of six sectors of the driver to obtain four action times of the given voltage of different sectors; assuming a given voltage is in the first sector, the duration of the given voltage acting on vector 100 is set to x 1 Setting the application time of a given voltage on vector 110 to x 2 Setting the application time of a given voltage on vector 010 to x 3 Setting the application time of a given voltage on vector 101 to x 4 Then the related vectors of the given voltage in the first sector and the second sector participate in the decomposition to obtain the voltage vector U under the two-phase static coordinate system alpha beta α1 、U β1 (ii) a The voltage vector is used as the input of the modulation wave calculation module, the conduction sequence of the switch unit is adjusted, the related vectors of the first sector and the second sector are redistributed, and the action time x on the vector 100 is changed 1 Redefining the action time as 010 vector action time x 3 Redefined as action time on 100 vectors, action time x on vector 110 2 Time of action x on sum vector 101 4 Keeping the same; observing a waveform diagram in a first sector modulation interval of the voltage type three-phase inverter, and modulating to obtain the switching time of a drive topological structure, wherein the switching time of the first sector is a 1 ＝x 2 +x 3 +x 4 a 2 ＝x 1 +x 2 a 3 ＝x 4 (ii) a And analogizing in turn, each sector has the same calculation to obtain the switching time a of four voltage vectors after each sector in the modulation interval decomposes the given voltage of the driver 1 、a 2 、a 3 ；
And 4, step 4: and voltage three-vector synthesis is adopted for the overmodulation interval to obtain the switching time of the overmodulation interval: decomposing the given voltage in each sector according to a topological voltage vector diagram of six sectors of the driver to obtain three action times of the given voltage of different sectors; arranging all the obtained action time in sequence, and setting the action time of the given voltage on the vector 100 to be x on the assumption that the given voltage is in the first sector 1 Setting the application time of a given voltage on vector 110 to x 2 Setting the application time of a given voltage on vector 010 to x 3 Then the related vectors of the given voltage in the first sector and the second sector participate in the decomposition to obtain the voltage vector U under the two-phase static coordinate system alpha beta α 、U β (ii) a The voltage vector is used as the input of a modulation wave calculation module to generate a waveform, the first sector and the related vectors of the second sector are arranged according to the action time sequence, the waveform diagram of the overmodulation interval of the first sector of the voltage type three-phase inverter is observed and modulated, and the switching time a of the topological structure of the voltage type three-phase inverter is obtained 1 ＝x 2 +x 3 、a 2 ＝x 1 +x 2 、a 3 =0; and analogizing in turn, each sector has the same calculation, and the switching time a of three voltage vectors after each sector of the overmodulation interval is decomposed for the given voltage of the drive is obtained 1 、a 2 、a 3 ；
And 5: and finishing SVPWM (space vector pulse width modulation) common-mode voltage suppression based on change in a synthesis mode: and according to a switching time oscillogram drawn by redistribution of the six sector areas, the switching time of a modulation interval and an overmodulation interval is modulated through experiments, and the suppression of the common-mode voltage of the voltage type three-phase inverter is realized.
2. The SVPWM common-mode voltage suppression method based on synthesis mode variation as claimed in claim 1, wherein said step 3 of obtaining the action time of the modulation interval by using four-vector synthesis of voltage within the modulation interval is to rearrange the action time, draw a waveform diagram to obtain the switching time of the modulation interval, taking the first sector voltage as an example, comprising the steps of:
(3.1) given the voltage vector decomposition expression: the first sector voltage vector decomposition expression is:
Figure FDA0003775173770000021
wherein:
Figure FDA0003775173770000022
setting a voltage for the driver; x is a radical of a fluorine atom 1 、x 2 、x 3 、x 4 Four action times for a given voltage after the first sector decomposition, wherein the action time of the given voltage on the vector 010 is x 1 Setting the application time of a given voltage on vector 110 to x 2 Setting the application time of a given voltage on vector 100 to x 3 Setting the application time of a given voltage on vector 101 to x 4 ；
Figure FDA0003775173770000031
Is a sector voltage vector corresponding to the resolution of the given drive voltage in the first sector and two sectors adjacent to the first sector;
(3.2) setting limiting conditions: the first sector voltage vector calculation constraints are:
Figure FDA0003775173770000032
in the formula, x 1 、x 2 、x 3 、x 4 For a given voltageFour action times after the first sector decomposition;
(3.3) calculating a voltage vector: performing module value calculation on the given voltage in the first sector to obtain module value
Figure FDA0003775173770000033
Substituting the transformation angle to calculate a voltage vector under the two-phase static coordinate system alpha beta: u shape α1 、U β1
Figure FDA0003775173770000034
In the formula of U α1 For a component, U, in a two-phase stationary coordinate system alpha after a given voltage decomposition β1 The component under a two-phase static coordinate system beta after the given voltage decomposition is taken as the component;
(3.4) obtaining the action time of the given voltage of the first sector: substituting the limiting conditions into a given voltage vector decomposition expression of the first sector to obtain the action time of the first sector:
Figure FDA0003775173770000035
in the formula, x 1 For a given duration of application of voltage to vector 010, x 2 For a given voltage applied to vector 110, x 3 To set the application time, x, of a given voltage on vector 100 4 To set the application time for a given voltage to act on vector 101,
Figure FDA0003775173770000036
is the standard vector length;
(3.5) redistribution of the conduction order of the switching cells: the action time x on the vector 100 1 Redefined as the time of action on the 010 vector, x on the 010 vector 3 Redefined as action time on 100 vectors, action time x on vector 110 2 And the effect on vector 101X is 4 Keeping the same; the action time x of redistribution after decomposing the obtained given voltage vector of the first sector driver 1 、x 2 、x 3 、x 4 Combining with carrier waves, drawing a waveform diagram to obtain switching time a based on a voltage type three-phase inverter topological structure 1 、a 2 、a 3 And analyzing the oscillogram to obtain:
a 1 ＝x 2 +x 3 +x 4 a 2 ＝x 1 +x 2 a 3 ＝x 4
in the formula, a 1 、a 2 、a 3 Switching time, x, based on voltage-type three-phase inverter topology 1 、x 2 、x 3 、x 4 Four action times after the decomposition of the given voltage in the first sector are given;
(3.6) obtaining a relation between the switching time and a given voltage vector: combining the relation between the switching time and the action time of the first sector and the relation between the given voltage vector and the action time to obtain a relation:
Figure FDA0003775173770000041
in the formula, a 1 、a 2 、a 3 For switching time based on voltage type three-phase inverter topology, U α1 、U β1 The driver is given a vector obtained under a two-phase stationary coordinate system alpha beta after voltage decomposition,
Figure FDA0003775173770000042
obtaining the switching time within the maximum voltage utilization interval of the first sector for the standard vector length, and returning to the step (3.1) for calculating the switching time of the next sector;
(3.7) obtaining the switching time of the given voltage of all sectors: and (3) circularly executing the steps (3.1) - (3.6), sequentially executing other sectors according to the same method, and calculating the relation between the switching time of all sectors in the modulation area and the given voltage vector.
3. The SVPWM common-mode voltage suppression method based on synthesis mode variation according to claim 1, wherein said step 4 of obtaining the acting time of the overmodulation region by voltage three-vector synthesis is to arrange the acting time in sequence, draw a waveform diagram to obtain the switching time of the overmodulation region, taking the first sector voltage as an example, comprising the following steps:
(4.1) given the voltage vector decomposition expression: the first sector voltage vector decomposition expression is:
Figure FDA0003775173770000043
wherein:
Figure FDA0003775173770000044
setting a voltage for the driver; x is the number of 1 、x 2 、x 3 Four application times after the first sector decomposition for a given voltage, wherein the application time of the given voltage on the vector 010 is x 1 Setting the application time of a given voltage on vector 110 to x 2 Setting the application time of a given voltage on vector 100 to x 3 ；
Figure FDA0003775173770000051
Is a voltage vector of a given voltage which is decomposed in a first sector and a second sector;
(4.2) calculating a voltage vector: performing module value calculation on the given voltage in the first sector to obtain module value
Figure FDA0003775173770000052
Substituting the transformation angle to calculate a voltage vector under the two-phase static coordinate system alpha beta: u shape α 、U β
Figure FDA0003775173770000053
In the formula of U α For a component, U, in a two-phase stationary coordinate system alpha after a given voltage decomposition β The component under a two-phase static coordinate system beta after the given voltage decomposition is taken as the component;
(4.3) limiting conditions: the first sector voltage vector calculation constraints are:
Figure FDA0003775173770000054
in the formula, x 1 、x 2 、x 3 For three active times, U, after the first sector has been divided for a given voltage α For a component, U, in a two-phase stationary coordinate system alpha after a given voltage decomposition β The component under a two-phase static coordinate system beta after the given voltage decomposition is taken as the component;
(4.4) obtaining the action time of the given voltage of the first sector: substituting the limiting conditions into a given voltage vector decomposition expression of the first sector to obtain the action time of the first sector:
Figure FDA0003775173770000055
in the formula, x 1 For a given duration of application of voltage to vector 010, x 2 For a given voltage applied to vector 110, x 3 To set the application time for a given voltage to be applied to vector 100,
Figure FDA0003775173770000056
is the standard vector length;
(4.5) decomposing the obtained first sector given voltage vector to obtain action time x 1 、x 2 、x 3 Arranging according to the decomposition sequence, combining with carrier waves, drawing a waveform diagram to obtain the switching time a based on the topology structure of a single driver 1 、a 2 、a 3 And analyzing the image to obtain:
a 1 ＝x 2 +x 3 a 2 ＝x 1 +x 2 a 3 ＝0
(4.6) combining the relation of the switching time and the action time of the first sector and the relation of the given voltage vector and the action time to obtain a relation:
Figure FDA0003775173770000061
in the formula, a 1 、a 2 、a 3 For switching time based on single driver topology, U α 、U β Returning to the step (4.1) to calculate the switching time of the next sector for the vector obtained under the two-phase static coordinate system alpha beta after the given voltage is decomposed;
(4.7) obtaining the switching time of the given voltage of all sectors: and (4.1) to (4.6) are executed in a circulating way, and other sectors are sequentially executed according to the same method, so that the switching time of the given voltage of all the sectors of the overmodulation region is obtained.
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