CN104935196A - A space vector modulation method for dual three-level inverter system zero sequence voltage elimination - Google Patents

Abstract

A kind of space vector modulating method that dual three-level inverter system residual voltage is eliminated, belongs to inverter system space vector modulating method. The action time for adjusting zero vector in each switch periods makes the average residual voltage 0 of dual three-level inverter system, it is decoupled using unified fast algorithm and space voltage vector, reference voltage vector is decomposed into two equal in magnitude, direction 60 ° of equivalent reference voltage vector each other, and the amplitude of two equivalent reference voltage vectors is the amplitude of reference voltage vector Times, and individually generated by two diode-clamped three-level inverters, realize the elimination to the instantaneous value of dual three-level inverter system residual voltage. Method And Principle is simple, it is clear in structure, it is decoupled using unified fast algorithm and space voltage vector, two three-level inverters in dual three-level inverter system are made to work in the powering mode of single DC voltage source, effectively simplify topological structure and reduce cost, realizes the four quadrant running for opening winding asynchronous motor.

Description

The space vector modulating method that dual three-level inverter system residual voltage is eliminated

Technical field

The present invention relates to a kind of inverter system space vector modulating method, the space vector modulating method of particularly a kind of dual three-level inverter system residual voltage elimination.

Background technology

In recent years, the harmonic wave of output voltage content of multi-electrical level inverter is low, little to the switch stress of semiconductor device, obtains apply more and more widely in the powerful occasion of middle high-pressure.Compared with diode clamp type, striding capacitance type, H bridge cascaded inverter, when switching device quantity is equal, more level number can be provided to load owing to opening winding asynchronous motor both-end cascade type DC-to-AC converter, produce less output voltage, current harmonics, so make it more outstanding at the application potential of multi-electrical level inverter field and transmission field.But the residual voltage problem that this inverter topology produces when single direct voltage source is powered remains the focus of numerous scholar's research, wherein especially based on the research of two two level and dual three-level inverter.For this problem, the method much eliminated about two two level and dual three-level inverter residual voltage and modulation strategy is had to be suggested.

When driving winding asynchronous motor dual three-level inverter and being operated in single direct voltage source powering mode, internal system can form loop, now system can produce very large zero-sequence current under the effect of residual voltage, thus form the circulation of internal system, the harmonic content of electric machine phase current is increased, and the insulation of winding electric machine is opened in infringement, thus affects the normal operation of equipment, so need to suppress the residual voltage of system, guarantee that system works is in good running status.The existing removing method to dual three-level inverter system residual voltage mainly contains following three kinds: (1) adopts independently direct voltage source to power to two three-level inverters, make system zero sequence voltage not become loop in internal system, thus do not produce zero-sequence current; (2) utilizing the method for unified fast algorithm and space voltage vector 180 ° of decoupling zeros, by adjusting the action time of zero vector, making its residual voltage mean value that each inverter produces in each switch periods be zero; (3) when dual three-level inverter is operated in single direct voltage source powering mode, the method for staggered clamper is utilized to make the mean value of load three-phase phase voltage sum in each switch periods be zero.

Analysis is carried out to these above control methods known, the independent direct current voltage source that method (1) adopts powers to two three-level inverters, although now the residual voltage of system is non-vanishing, very large residual voltage is there is in system, but because the direct voltage source of two inverters is isolated, internal system does not form loop, so now the zero-sequence current of system is 0, on the operation of system without impact, but this method can increase the equipment cost of system, and be difficult to the four quadrant running realizing motor; Method (2) and method (3) are just dynamically eliminated the residual voltage of dual three-level inverter system from average, and the amplitude of the residual voltage in inverter system is still very high.

Summary of the invention

The object of the invention is the space vector modulating method that a kind of dual three-level inverter system residual voltage will be provided to eliminate, realize the elimination of the instantaneous value to dual three-level inverter system residual voltage.

The object of the present invention is achieved like this: this space vector modulating method is, be decomposed into two equal and opposite in directions, the direction equivalent reference voltage vector of 60 ° each other with reference to voltage vector, and the amplitude of these two equivalent reference voltage vectors is the amplitude of reference voltage vector doubly, individually produced by two diode-clamped three-level inverter, then unified fast algorithm is utilized two corresponding for these two equivalent reference voltage vectors level component to be converted into the imaginary switching over moment of corresponding three-phase brachium pontis separately and to obtain corresponding effective acting time, and then obtain the actual switch switching instant of the three-phase brachium pontis of two two level component under space voltage vector modulation, finally the on off state that uncorrecting obtains corresponding two equivalent reference voltage vectors is carried out to the on off state of these two two level resolutes, complete the modulation of dual three-level inverter, realize effective elimination of dual three-level inverter system residual voltage.

Specific implementation step is:

Step one: with reference to voltage vector U _refbe decomposed into two equal and opposite in directions, the direction equivalent reference voltage vector U of 60 ° each other _ref1and U _ref2, and $\left|U_{ref1}\right|=\left|U_{ref2}\right|=\left|U_{ref}\right|/\sqrt{3};$

Step 2: by two equivalent reference voltage vector U _ref1and U _ref2α axle component U _{ref α 1}, U _{ref α 2}with beta-axis component U _{ref β 1}, U _{ref β 2}utilize the three-phase component U that the matrixing of following formula obtains in three-phase static coordinate system abc _refa1, U _refb1, U _refc1and U _refa2, U _refb2, U _refc2:

$\left[\begin{array}{c}{U}_{refax}\\ U_{refbx}\\ U_{refcx}\end{array}\right]=\left[\begin{array}{cc}1& 0\\ -\frac{1}{2}& \frac{\sqrt{3}}{2}\\ \frac{1}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{U}_{ref\mathrm{\α}x}\\ U_{ref\mathrm{\β}x}\end{array}\right]$

Wherein, x ∈ (1,2);

Step 3: determine two equivalent reference voltage vector U according to following table _ref1and U _ref2sector in the 3 level space vector figure of place:

Sector S	Criterion
		1	U refax>0&U refbx<0&U refcx<0
2	U refax>0&U refbx>0&U refcx<0
		3	U refax<0&U refbx>0&U refcx<0
4	U refax<0&U refbx>0&U refcx>0
		5	U refax<0&U refbx<0&U refcx>0
6	U refax>0&U refbx<0&U refcx>0

Wherein, x ∈ (1,2);

Step 4: according to these two equivalent reference voltage vector U _ref1and U _ref2the center vector U of sector, place _base1and U _base2, by these two equivalent reference voltage vector U _ref1and U _ref2carry out revising decomposing and obtain center vector U corresponding separately _base1, U _base2with two level resolute U ＇ _ref1, U ＇ _ref2, and the three-phase separate value of the center vector that different sector is corresponding in 3 level space vector figure is different, shown in table specific as follows:

Sector S	U baseax	U basebx	U basecx
				1	U dc/6	﹣U dc/12	﹣U dc/12
2	U dc/12	U dc/12	﹣U dc/6
				3	﹣U dc/12	U dc/6	﹣U dc/12
4	﹣U dc/6	U dc/12	U dc/12
				5	﹣U dc/12	U dc/6	﹣U dc/12
6	U dc/12	﹣U dc/6	U dc/12

Wherein, x ∈ (1,2), U _dcrepresent 2 times of three-level inverter DC voltage;

Step 5: utilize following formula can obtain two level resolute U ＇ _ref1, U ＇ _ref2the value U ＇ of three-phase corresponding separately in three-phase static coordinate system abc _refax, U ＇ _refbx, U ＇ _refcx:

U＇ _refx＝U _refx-U _basex

U _refx＝[U _refaxU _refbxU _refcx] ^T

U＇ _refx＝[U＇ _refaxU＇ _refbxU＇ _refcx] ^T

U _basex＝[U _baseaxU _basebxU _basecx] ^T

U＇ _refax＝U _refax-U _baseax

U＇ _refbx＝U _refbx-U _basebx

U＇ _refcx＝U _refcx-U _basecx

Wherein, x ∈ (1,2);

Step 6: utilize unified fast algorithm, by two two level resolute U ＇ _ref1, U ＇ _ref2the value of three-phase can obtain the imaginary switching over moment T of the three-phase brachium pontis of two corresponding separately level resolutes after following formula process _as1, T _bs1, T _cs1and T _as2, T _bs2, T _cs2:

$T_{psq}=\frac{2\·U_{refpq}^{\′}}{U_{dc}}\·T_s$

T _maxq＝max(T _asq,T _bsq,T _csq)

T _minq＝min(T _asq,T _bsq,T _csq)

T _effq＝T _maxq-T _minq

Wherein, p ∈ (a, b, c), q ∈ (1,2), T _maxand T _minmaximum in the imaginary switching over moment representing three-phase brachium pontis respectively and minimum value, T _efffor effective acting time, so-called effective acting time is that inverter is at a switch periods T _sthe output level number asynchronous time period of interior three-phase brachium pontis, because only have when the three-phase brachium pontis output level number of inverter is different, inverter ability power stage;

Step 7: utilize following formula can obtain two two level resolute U ＇ _ref1, U ＇ _ref2the actual switch switching instant T of the three-phase brachium pontis under space voltage vector modulation _ga1, T _gb1, T _gc1and T _ga2, T _gb2, T _gc2:

T _gxy＝T _axy+T _offsety

T _0y＝T _s/2-T _effy

$T_{offsety}=\frac{T_{0y}}{2}-T_{\min y}$

Wherein, x ∈ (a, b, c), y ∈ (1,2), T _offsetrepresent shift time;

Step 8: the on off state of two the two level resolutes obtained by step 7, it only has (0,1) two kinds, if drive two diode-clamped three-level inverter work to carry out uncorrecting with regard to needing to the on off state of revised two two sectors, level resolute place, namely add one group of on off state of place sector zone center vector; According to the sector partitioning method of step 2 and step 3, the on off state of the center vector that 1 ~ 6 sector is corresponding is as shown in the table:

Sector S	Center vector on off state
		1	100
2	110
		3	010
4	011

5	001
		6	101

Wherein, 0,1,2 represent the every phase n of three-level inverter, o, p output level respectively, and the on off state of the center vector that the different sectors that in utilization, tabular goes out are corresponding just can complete uncorrecting process to the on off state of all two two level resolutes;

Step 9: the on off state obtained according to step 8, the duty ratio of the switching signal of the first inverter in calculating dual three-level inverter and each road power switch pipe of the second inverter;

Step 10: the timer 1 of allocating digital signal processor, for generation of the triangle carrier signal of 5kHz high frequency;

Step 11: the switching signal duty ratio of the three-level inverter Zhong Ge road power tube switch obtained according to step 9 calculates and upgrades the value of comparand register in digital signal processor, thus 12 tunnel pulses are produced in the task manager A and task manager B of digital signal processor, recycling field programmable gate array carries out negate to the 12 tunnel pulses sent from digital signal processor, obtain two the diode-clamped three-level inverter work of 24 tunnel pulsed drive, complete the space vector modulation process to dual three-level inverter, realize the elimination to dual three-level inverter system residual voltage.

The modulation degree m of definition _afor:

$m_a=\frac{2\·U_{ref}}{U_{dc}}.$

Beneficial effect, owing to have employed such scheme, without the need to making the action time by adjusting zero vector in each inverter its residual voltage mean value that each inverter produces in each switch periods be zero, without the need to dynamically suppressing the residual voltage of system in each switch periods, the method of unified fast algorithm and space voltage vector decoupling zero is utilized to be decomposed into two equal and opposite in directions with reference to voltage vector, the direction equivalent reference vector of 60 ° each other, and individually produced by two inverters, can be simple, effective realization is to the elimination of the instantaneous value of dual three-level inverter system residual voltage.

Advantage: Method And Principle is simple, clear in structure, only need utilize the principle of unified fast algorithm and space voltage vector decoupling zero and method that in dual three-level inverter system two three-level inverters just can be made to be operated in the powering mode of single direct voltage source, effective simplification topological structure and reducing costs, is easy to the four quadrant running realizing out winding asynchronous motor.

Accompanying drawing explanation

Fig. 1 is a kind of space vector modulation algorithm flow chart eliminated based on dual three-level inverter system residual voltage newly of the present invention.

Fig. 2 is the main topological diagram of dual three-level inverter being in common DC bus structure of the present invention.

Fig. 3 is dual three-level inverter of the present invention 60 ° of space voltage vector decoupling principle figure.

Fig. 4 is the se ctor partition figure of three-level inverter space voltage vector of the present invention distribution and correspondence.

Fig. 5 is U of the present invention _ref1switching pulse corresponding to three-phase reference signal instantaneous value and effective switching time relation principle figure.

Fig. 6 is U of the present invention _ref1the switching pulse that three-phase reference signal instantaneous value when being in 2 sector is corresponding and effective switching time graph of a relation.

Fig. 7 is U of the present invention _ref2the switching pulse that three-phase reference signal instantaneous value when being in 4 sector is corresponding and effective switching time graph of a relation.

Fig. 8 is modulation degree m of the present invention _aelectric machine phase current when=0.9 under different powering mode and phase voltage experimental waveform figure.

Fig. 9 is modulation degree m of the present invention _aelectric machine phase current when=0.5 under different powering mode and phase voltage test waveform figure.

Figure 10 is that modulation degree of the present invention is respectively m _a=0.9 and m _adual three-level inverter system residual voltage test waveform figure when=0.5 under independent direct current voltage fed pattern.

Embodiment

Be described further below in conjunction with 1 pair, accompanying drawing institute of the present invention execution mode, a kind of space vector modulating method dual three-level inverter system residual voltage being carried out to effectively elimination newly described in present embodiment, for 60 ° of space vector Decoupled Model, the method is: be first decomposed into two equal and opposite in directions, the direction equivalent reference voltage vector of 60 ° each other with reference to voltage vector, and the amplitude of these two equivalent reference voltage vectors is reference voltage vector amplitude doubly, and individually produced by two diode-clamped three-level inverter, then unified fast algorithm is utilized two corresponding for these two equivalent reference voltage vectors level component to be converted into the imaginary switching over moment of corresponding three-phase brachium pontis separately and to obtain corresponding effective acting time, and then obtain the actual switch switching instant of the three-phase brachium pontis of these two two level component under space voltage vector modulation, finally the on off state that uncorrecting obtains corresponding two equivalent reference voltage vectors is carried out to the on off state of these two two level resolutes, complete the modulated process to dual three-level inverter, realize the effective elimination to dual three-level inverter system residual voltage.

The method is realized by digital signal processor and field programmable gate array, specifically comprises the following steps:

Step one: with reference to voltage vector U _refbe decomposed into two equal and opposite in directions, the direction equivalent reference voltage vector U of 60 ° each other _ref1and U _ref2, and $\left|U_{ref1}\right|=\left|U_{ref2}\right|=\left|U_{ref}\right|/\sqrt{3};$

Step 2: by two equivalent reference voltage vector U _ref1and U _ref2α axle component U _{ref α 1}, U _{ref α 2}with beta-axis component U _{ref β 1}, U _{ref β 2}utilize the three-phase component U that the matrixing of following formula obtains in three-phase static coordinate system abc _refa1, U _refb1, U _refc1and U _refa2, U _refb2, U _refc2:

$\left[\begin{array}{c}{U}_{refax}\\ U_{refbx}\\ U_{refcx}\end{array}\right]=\left[\begin{array}{cc}1& 0\\ -\frac{1}{2}& \frac{\sqrt{3}}{2}\\ \frac{1}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{U}_{ref\mathrm{\α}x}\\ U_{ref\mathrm{\β}x}\end{array}\right]$

Wherein, x ∈ (1,2);

Step 3: judge two equivalent reference voltage vector U according to following table _ref1and U _ref2sector in the 3 level space vector figure of place:

Sector S	Criterion
		1	U refax>0&U refbx<0&U refcx<0
2	U refax>0&U refbx>0&U refcx<0
		3	U refax<0&U refbx>0&U refcx<0
4	U refax<0&U refbx>0&U refcx>0
		5	U refax<0&U refbx<0&U refcx>0
6	U refax>0&U refbx<0&U refcx>0

Wherein, x ∈ (1,2);

Step 4: according to these two equivalent reference voltage vector U _ref1and U _ref2the center vector U of sector, place _base1and U _base2, by these two equivalent reference voltage vector U _ref1and U _ref2carry out revising decomposing and obtain center vector U corresponding separately _base1, U _base2with two level resolute U ＇ _ref1, U ＇ _ref2, and the three-phase separate value of the center vector that different sector is corresponding in 3 level space vector figure is different, shown in table specific as follows:

Sector S	U baseax	U basebx	U basecx
				1	U dc/6	﹣U dc/12	﹣U dc/12
2	U dc/12	U dc/12	﹣U dc/6
				3	﹣U dc/12	U dc/6	﹣U dc/12
4	﹣U dc/6	U dc/12	U dc/12
				5	﹣U dc/12	U dc/6	﹣U dc/12
6	U dc/12	﹣U dc/6	U dc/12

Wherein, x ∈ (1,2), U _dcrepresent 2 times of three-level inverter DC voltage;

Step 5: utilize following formula can obtain two level resolute U ＇ _ref1, U ＇ _ref2the value U ＇ of three-phase corresponding separately in three-phase static coordinate system abc _refax, U ＇ _refbx, U ＇ _refcx:

U＇ _refx＝U _refx-U _basex

U _refx＝[U _refaxU _refbxU _refcx] ^T

U＇ _refx＝[U＇ _refaxU＇ _refbxU＇ _refcx] ^T

U _basex＝[U _baseaxU _basebxU _basecx] ^T

U＇ _refax＝U _refax-U _baseax

U＇ _refbx＝U _refbx-U _basebx

U＇ _refcx＝U _refcx-U _basecx

Wherein, x ∈ (1,2);

Step 6: utilize unified fast algorithm, by two two level resolute U ＇ _ref1, U ＇ _ref2the value of three-phase can obtain the imaginary switching over moment T of the three-phase brachium pontis of two corresponding separately level resolutes after following formula process _as1, T _bs1, T _cs1and T _as2, T _bs2, T _cs2:

$T_{psq}=\frac{2\·U_{refpq}^{\′}}{U_{dc}}\·T_s$

T _maxq＝max(T _asq,T _bsq,T _csq)

T _minq＝min(T _asq,T _bsq,T _csq)

T _effq＝T _maxq-T _minq

Wherein, p ∈ (a, b, c), q ∈ (1,2), T _maxand T _minmaximum in the imaginary switching over moment representing three-phase brachium pontis respectively and minimum value, T _efffor effective acting time, so-called effective acting time, refer to inverter at a switch periods T _sthe output level number asynchronous time period of interior three-phase brachium pontis, because only have when the three-phase brachium pontis output level number of inverter is different, inverter ability power stage;

Step 7: utilize following formula can obtain two two level resolute U ＇ _ref1, U ＇ _ref2the actual switch switching instant T of the three-phase brachium pontis under space voltage vector modulation _ga1, T _gb1, T _gc1and T _ga2, T _gb2, T _gc2:

T _gxy＝T _axy+T _offsety

T _0y＝T _s/2-T _effy

$T_{offsety}=\frac{T_{0y}}{2}-T_{\min y}$

Wherein, x ∈ (a, b, c), y ∈ (1,2), T _offsetrepresent shift time;

Step 8: the on off state of two the two level resolutes obtained by step 7, it only has (0,1) two kinds, if drive two diode-clamped three-level inverter work to carry out uncorrecting with regard to needing to the on off state of revised two two sectors, level resolute place, namely add one group of on off state of place sector zone center vector.According to the sector partitioning method of step 2 and step 3, the on off state of the center vector that 1 ~ 6 sector is corresponding is as shown in the table:

Sector S	Center vector on off state
		1	100
2	110
		3	010
4	011
		5	001
6	101

Wherein, 0,1,2 represent the every phase n of three-level inverter, o, p output level respectively, and the on off state of the center vector that the different sectors that in utilization, tabular goes out are corresponding just can complete uncorrecting process to the on off state of all two two level resolutes;

Step 9: the on off state obtained according to step 8, the duty ratio of the switching signal of the inverter 1 in calculating dual three-level inverter and each road power switch pipe of inverter 2;

Step 10: the timer 1 of allocating digital signal processor, for generation of the triangle carrier signal of 5kHz high frequency;

Step 11: the switching signal duty ratio of the three-level inverter Zhong Ge road power tube switch obtained according to step 9 calculates and upgrades the value of comparand register in digital signal processor, thus 12 tunnel pulses are produced in the task manager A and task manager B of digital signal processor, recycling field programmable gate array carries out negate to the 12 tunnel pulses sent from digital signal processor, obtain two the diode-clamped three-level inverter work of 24 tunnel pulsed drive, complete the space vector modulation process to dual three-level inverter, realize the elimination to dual three-level inverter system residual voltage.

Wherein, for verifying the eradicating efficacy of algorithm described herein to dual three-level inverter system residual voltage, building Experimental Hardware platform especially and having studied, and adopted the control mode of constant voltage and frequency ratio (V/F) to control out the operation of winding asynchronous motor.From experimental result, when adopting 60 ° of space voltage vector decoupling zero modulation algorithms to control the operation of dual three-level inverter system, when system works is in high modulation region, the phase voltage of motor is five level, the phase voltage of system works motor when low-key system region is three level, and the output waveform of electric machine phase current under high and low modulation degree is good, the instantaneous value of the residual voltage of system is 0 substantially, therefore, this modulation strategy simply, effectively can realize the elimination to dual three-level inverter system residual voltage instantaneous value.

Claims (3)

1. the space vector modulating method of a dual three-level inverter system residual voltage elimination, it is characterized in that: this space vector modulating method is, be decomposed into two equal and opposite in directions, the direction equivalent reference voltage vector of 60 ° each other with reference to voltage vector, and the amplitude of these two equivalent reference voltage vectors is the amplitude of reference voltage vector doubly, individually produced by two diode-clamped three-level inverter, then unified fast algorithm is utilized two corresponding for these two equivalent reference voltage vectors level component to be converted into the imaginary switching over moment of corresponding three-phase brachium pontis separately and to obtain corresponding effective acting time, and then obtain the actual switch switching instant of the three-phase brachium pontis of two two level component under space voltage vector modulation, finally the on off state that uncorrecting obtains corresponding two equivalent reference voltage vectors is carried out to the on off state of these two two level resolutes, complete the modulation of dual three-level inverter, realize effective elimination of dual three-level inverter system residual voltage.

2. the space vector modulating method of a kind of dual three-level inverter system residual voltage elimination according to claim 1, is characterized in that: the concrete steps of realization are:

Step one: with reference to voltage vector U _refbe decomposed into two equal and opposite in directions, the direction equivalent reference voltage vector U of 60 ° each other _ref1and U _ref2, and $\left|U_{ref1}\right|=\left|U_{ref2}\right|=\left|U_{ref}\right|/\sqrt{3};$

Step 2: by two equivalent reference voltage vector U _ref1and U _ref2α axle component U _{ref α 1}, U _{ref α 2}with beta-axis component U _{ref β 1}, U _{ref β 2}utilize the three-phase component U that the matrixing of following formula obtains in three-phase static coordinate system abc _refa1, U _refb1, U _refc1and U _refa2, U _refb2, U _refc2:

$\left[\begin{array}{c}{U}_{refax}\\ U_{refbx}\\ U_{refcx}\end{array}\right]=\left[\begin{array}{cc}1& 0\\ -\frac{1}{2}& \frac{\sqrt{3}}{2}\\ \frac{1}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{U}_{ref\mathrm{\α}x}\\ U_{ref\mathrm{\β}x}\end{array}\right]$

Wherein, x ∈ (1,2);

Step 3: judge two equivalent reference voltage vector U according to following table _ref1and U _ref2sector in the 3 level space vector figure of place:

Sector S Criterion 1 U _refax>0&U _refbx<0&U _refcx<0 2 U _refax>0&U _refbx>0&U _refcx<0 3 U _refax<0&U _refbx>0&U _refcx<0 4 U _refax<0&U _refbx>0&U _refcx>0 5 U _refax<0&U _refbx<0&U _refcx>0 6 U _refax>0&U _refbx<0&U _refcx>0

Wherein, x ∈ (1,2);

Step 4: according to these two equivalent reference voltage vector U _ref1and U _ref2the center vector U of sector, place _base1and U _base2, by these two equivalent reference voltage vector U _ref1and U _ref2carry out revising decomposing and obtain center vector U corresponding separately _base1, U _base2with two level resolute U ＇ _ref1, U ＇ _ref2, and the three-phase separate value of the center vector that different sector is corresponding in 3 level space vector figure is different, shown in table specific as follows:

Sector S U _baseax U _basebx U _basecx

1 U _dc/6 ﹣U _dc/12 ﹣U _dc/12 2 U _dc/12 U _dc/12 ﹣U _dc/6 3 ﹣U _dc/12 U _dc/6 ﹣U _dc/12 4 ﹣U _dc/6 U _dc/12 U _dc/12 5 ﹣U _dc/12 U _dc/6 ﹣U _dc/12 6 U _dc/12 ﹣U _dc/6 U _dc/12

Wherein, x ∈ (1,2), U _dcrepresent 2 times of three-level inverter DC voltage;

Step 5: utilize following formula can obtain two level resolute U ＇ _ref1, U ＇ _ref2the value U ＇ of three-phase corresponding separately in three-phase static coordinate system abc _refax, U ＇ _refbx, U ＇ _refcx:

U＇ _refx＝U _refx-U _basex

U _refx＝[U _refaxU _refbxU _refcx] ^T

U＇ _refx＝[U＇ _refaxU＇ _refbxU＇ _refcx] ^T

U _basex＝[U _baseaxU _basebxU _basecx] ^T

U＇ _refax＝U _refax-U _baseax

U＇ _refbx＝U _refbx-U _basebx

U＇ _refcx＝U _refcx-U _basecx

Wherein, x ∈ (1,2);

Step 6: utilize unified fast algorithm, by these two two level resolute U ＇ _ref1, U ＇ _ref2the value of three-phase can obtain the imaginary switching over moment T of the three-phase brachium pontis of two corresponding separately level resolutes after following formula process _as1, T _bs1, T _cs1and T _as2, T _bs2, T _cs2:

$T_{psq}=\frac{2\&CenterDot;U_{refpq}^{\&prime;}}{U_{dc}}\&CenterDot;T_s$

T _maxq＝max(T _asq,T _bsq,T _csq)

T _minq＝min(T _asq,T _bsq,T _csq)

T _effq＝T _maxq-T _minq

Wherein, p ∈ (a, b, c), q ∈ (1,2), T _maxand T _minmaximum in the imaginary switching over moment representing three-phase brachium pontis respectively and minimum value, T _efffor effective acting time, so-called effective acting time, refer to inverter at a switch periods T _sthe output level number asynchronous time period of interior three-phase brachium pontis, because only have when the three-phase brachium pontis output level number of inverter is different, inverter ability power stage;

Step 7: utilize following formula can obtain two two level resolute U ＇ _ref1, U ＇ _ref2the actual switch switching instant T of the three-phase brachium pontis under space voltage vector modulation _ga1, T _gb1, T _gc1and T _ga2, T _gb2, T _gc2:

T _gxy＝T _axy+T _offsety

T _0y＝T _s/2-T _effy

$T_{offsety}=\frac{T_{0y}}{2}-T_{\min y}$

Wherein, x ∈ (a, b, c), y ∈ (1,2), T _offsetrepresent shift time;

Step 8: the on off state of two the two level resolutes obtained by step 7, it only has (0,1) two kinds, if drive two diode-clamped three-level inverter work to carry out uncorrecting with regard to needing to the on off state of revised two two sectors, level resolute place, namely add one group of on off state of place sector zone center vector.According to the sector partitioning method of step 2 and step 3, the on off state of the center vector that 1 ~ 6 sector is corresponding is as shown in the table:

Sector S Center vector on off state 1 100 2 110 3 010 4 011 5 001 6 101

Wherein, 0,1,2 represent the every phase n of three-level inverter, o, p output level respectively, and the on off state of the center vector that the different sectors that in utilization, tabular goes out are corresponding just can complete uncorrecting process to the on off state of all two two level resolutes;

Step 9: the on off state obtained according to step 8, the duty ratio of the switching signal of the inverter 1 in calculating dual three-level inverter and each road power switch pipe of inverter 2;

Step 10: the timer 1 of allocating digital signal processor, for generation of the triangle carrier signal of 5kHz high frequency;

Step 11: the switching signal duty ratio of the three-level inverter Zhong Ge road power tube switch obtained according to step 9 calculates and upgrades the value of comparand register in digital signal processor, thus 12 tunnel pulses are produced in the task manager A and task manager B of digital signal processor, recycling field programmable gate array carries out negate to the 12 tunnel pulses sent from digital signal processor, obtain two the diode-clamped three-level inverter work of 24 tunnel pulsed drive, complete the space vector modulation process to dual three-level inverter, realize the elimination to dual three-level inverter system residual voltage.

3. the space vector modulating method of a kind of dual three-level inverter system residual voltage elimination according to claim 1, is characterized in that: the modulation degree m of definition _afor:

$m_a=\frac{2\&CenterDot;U_{ref}}{U_{dc}}.$