CN112436752A - Inverter 12 sector virtual vector overmodulation strategy - Google Patents

Inverter 12 sector virtual vector overmodulation strategy Download PDF

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CN112436752A
CN112436752A CN202011213584.2A CN202011213584A CN112436752A CN 112436752 A CN112436752 A CN 112436752A CN 202011213584 A CN202011213584 A CN 202011213584A CN 112436752 A CN112436752 A CN 112436752A
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voltage vector
sector
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vector
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CN112436752B (en
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杨淑英
王顺
谢震
张兴
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Hefei University of Technology
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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
    • 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

Abstract

The invention relates to the field of inverter modulation, in particular to an inverter 12-sector virtual vector overmodulation strategy. According to the strategy, the corresponding virtual voltage vector is selected to synthesize the reference voltage vector through 12 sector judgment, the sector judgment mode is simpler and more novel, the modulation range of the algorithm is improved through an overmodulation technology while the output common mode voltage amplitude and the third harmonic of the inverter are restrained by a virtual voltage vector method, the overmodulation process is smooth, the output voltage fundamental wave amplitude is not lost, and the algorithm applicability is effectively enhanced.

Description

Inverter 12 sector virtual vector overmodulation strategy
Technical Field
The invention relates to the field of inverter modulation, in particular to an inverter 12-sector virtual vector overmodulation strategy.
Background
A three-phase voltage source inverter using a Pulse Width Modulation (PWM) technique is widely used in a motor driving system because of many advantages such as a simple control algorithm, high output quality, and good stability. The PWM inverter also brings problems such as shaft voltage, bearing current, electromagnetic interference and the like while improving the performance of output waveform, shortens the service life of the motor and influences the normal operation of other electronic equipment. Existing research has demonstrated that zero-sequence components in the output voltage of PWM inverters (i.e., common mode voltage) are the main cause of these negative effects. As inverters are developed to have high power and high frequency, the common mode voltage problem is also increased with the increase of the switching frequency, thereby threatening the safety and reliability of the whole system. Therefore, the problem of inverter common mode voltage suppression has been widely focused by scholars at home and abroad.
Reference 1: an article of "A Near-State PWM Method With Reduced Switching Losses and Reduced Common-Mode Voltage for Three-Phase Voltage Source Inverters" ("Adjacent State pulse Width modulation for Three-Phase Voltage Source inverter to reduce Switching Losses and Common Mode Voltage" (E.Un and A.M.Hava, IEEE Transactions on Industry Applications, vol.45, No.2, pp.782-793, March-april2009.) ("A.Un and A.M.Hava, institute of Electrical and electronics Engineers Industrial Applications, 2009, Vol.45, pp.2 Phase 782 793)). The article utilizes three adjacent non-zero vectors of reference voltage vectors to participate in synthesis, so that the amplitude of common-mode voltage is effectively inhibited to be
Figure BDA0002757012990000011
But the modulation range is limited to 0.6046-0.9069 due to the obvious 3-order harmonic component, so that the practical application is limited.
Reference 2: an article of "A Virtual Space Vector Modulation Technique for the Reduction of Common-Mode Voltages in Box magnet and Third-Order Component" ("K.Tian, J.Wang, B.Wu, Z.Cheng and N.R.Zargari, IEEE Transactions on Power Electronics, vol.31, No.1, pp.839-848, Jan.2016.) (" a Virtual voltage Vector Modulation Technique for reducing Common Mode voltage amplitude and Third harmonic content "(K.Tian, J.Wang, B.Wu, Z.Cheng and N.R.Zargari, J.Cheng and N.R.Zargari, institute of Electrical and Electronics Engineers, Vol. 2016, Vol.31, No.1 839 848)). The article selects virtual voltage vectors synthesized by basic vectors to participate in synthesizing reference voltage vectors, so that the amplitude of the common-mode voltage output by the inverter is reduced to
Figure BDA0002757012990000021
Meanwhile, the output common-mode voltage period volt-second quantity is controlled to be zero, the third harmonic component of the output common-mode voltage of the inverter is effectively suppressed, the modulation degree is reduced, and the algorithm is influencedAnd (4) application range.
In summary, the prior art has the following problems:
1. although the adjacent state synthesis method reported in reference 1 avoids using a zero vector to participate in synthesis, and effectively reduces the amplitude of the common mode voltage output by the inverter, the modulation range is greatly limited, and the method is not capable of controlling the third harmonic component in the common mode voltage, which brings difficulty to the design of the common mode filter.
2. The virtual voltage vector method reported in reference 2 can suppress both the common-mode voltage amplitude and the third harmonic component therein, but requires that the coordinate axis is rotated by 30 degrees and the traditional 6-sector discrimination method is used, the sector discrimination is complex, the innovation of virtual voltage vector is not highlighted, and meanwhile, the modulation degree is reduced to 0-0.7854 for suppressing the third harmonic component, and the practical application is limited.
Disclosure of Invention
The technical problem to be solved by the invention is how to use the basic voltage vector to synthesize the virtual voltage vector, and the corresponding virtual voltage vector is judged and selected to synthesize the reference voltage vector through 12 sectors, so that the sector judgment mode is simpler and more novel, the modulation range of the algorithm is improved through an overmodulation technology while the output common-mode voltage amplitude and the third harmonic of the inverter are inhibited by a virtual voltage vector method, the overmodulation process is smooth, the output voltage fundamental wave amplitude is not lost, and the algorithm applicability is effectively enhanced.
The invention aims to realize the technical scheme that the invention provides a 12-sector virtual vector overmodulation strategy of an inverter, and a three-phase two-level voltage type inverter topological structure related to the strategy comprises a direct current source E, a three-phase two-level voltage type inverter, a motor three-phase stator winding and a capacitor C1And a capacitor C2(ii) a The capacitor C1And a capacitor C2The direct current source E is connected between a direct current positive bus P and a direct current negative bus N after being connected in series; in the three-phase bridge arm of the three-phase two-level voltage type inverter, each phase of bridge arm comprises 2 switching tubes with anti-parallel diodes, namely the three-phase two-level voltage type inverter comprises 6 switching tubes with anti-parallel diodes in total, and the 6 switching tubes are respectively marked as switching tubes Sa1Switch tube Sa2Switch tube Sb1Switch tube Sb2Switch tube Sc1Switch tube Sc2；
The strategy comprises the following steps:
step 1, setting a switch state, a basic voltage vector and a virtual voltage vector;
recording the switch state signal of a-phase bridge arm of the three-phase two-level voltage type inverter as a switch state signal SaThe switching state signal of the b-phase bridge arm of the three-phase two-level voltage type inverter is a switching state signal SbThe switching state signal of the c-phase bridge arm of the three-phase two-level voltage type inverter is a switching state signal Sc(ii) a Switch state signal Sa、Sb、ScEqual to 0 or 1;
obtaining 6 basic voltage vectors according to the switching states of three-phase bridge arms of the three-phase two-level voltage type inverter, and respectively recording the basic voltage vectors as basic voltage vectors V1Base voltage vector V2Base voltage vector V3Base voltage vector V4Base voltage vector V5And a base voltage vector V 66 switching state combinations (S) corresponding to the basic voltage vectorsa、Sb、Sc) The specific states of (a) are as follows:
base voltage vector V1The corresponding switch state combination is (100);
base voltage vector V2The corresponding switch state combination is (110);
base voltage vector V3The corresponding switch state combination is (010);
base voltage vector V4The corresponding switch state combination is (011);
base voltage vector V5The corresponding switch state combination is (001);
base voltage vector V6The corresponding switch state combination is (101);
the 6 base voltage vectors are used to construct the following 9 virtual voltage vectors: virtual voltage vector V12Virtual voltage vector V23Virtual voltage vector V34Virtual voltageVector V45Virtual voltage vector V56Virtual voltage vector V61Virtual voltage vector V14Virtual voltage vector V25And virtual voltage vector V36；
Step 2, judging a sector;
on an alpha-beta axis static coordinate system, taking an alpha axis as a starting point, dividing the alpha axis into 12 sectors of 30 degrees in the anticlockwise direction from a first quadrant, and naming each sector as sector 1-sector 12 in a mode that the number of the sectors increases in the anticlockwise direction;
setting a reference voltage vector to be modulated of a three-phase two-level voltage type inverter as VrefReference voltage vector VrefThe projection components of the coordinate axes alpha and beta in the static coordinate system are respectively marked as the components V of the reference voltage vector alphaαAnd a reference voltage vector beta axis component VβFrom the reference voltage vector α -axis component VαAnd a reference voltage vector beta axis component VβCarry out a reference voltage vector VrefJudging the located sector;
of the 12 sectors, each sector uses 3 virtual voltage vectors vs. a reference voltage vector VrefSynthesizing, wherein 3 virtual voltage vectors relate to 4 basic voltage vectors;
the 3 virtual voltage vectors involved in each of the 12 sectors and the ordering are as follows:
sector 1: virtual voltage vector V61Virtual voltage vector V12Virtual voltage vector V36；
Sector 2: virtual voltage vector V12Virtual voltage vector V23Virtual voltage vector V36；
Sector 3: virtual voltage vector V12Virtual voltage vector V23Virtual voltage vector V14；
Sector 4: virtual voltage vector V23Virtual voltage vector V34Virtual voltage vector V14；
Sector 5: virtual voltage vector V23Virtual voltage vector V34Virtual voltage vector V25；
Sector 6: virtual voltage vector V34Virtual voltage vector V45Virtual voltage vector V25；
Sector 7: virtual voltage vector V34Virtual voltage vector V45Virtual voltage vector V36；
Sector 8: virtual voltage vector V45Virtual voltage vector V56Virtual voltage vector V36：
Sector 9: virtual voltage vector V45Virtual voltage vector V56Virtual voltage vector V14；
Sector 10: virtual voltage vector V56Virtual voltage vector V61Virtual voltage vector V14；
Sector 11: virtual voltage vector V56Virtual voltage vector V61Virtual voltage vector V25；
Sector 12: virtual voltage vector V61Virtual voltage vector V12Virtual voltage vector V25；
The 4 basic voltage vectors involved in each of the 12 sectors and the ordering are as follows:
sector 1: base voltage vector V6Base voltage vector V1Base voltage vector V2Base voltage vector V3；
Sector 2: base voltage vector V6Base voltage vector V1Base voltage vector V2Base voltage vector V3；
Sector 3: base voltage vector V1Base voltage vector V2Base voltage vector V3Base voltage vector V4；
Sector 4: base voltage vector V1Base voltage vector V2Base voltage vector V3Base voltage vector V4；
Sector 5: base voltage vector V2Base voltage vector V3Base voltage vector V4Base voltage vector V5；
Sector 6: base voltage vector V2Base voltage vector V3Base voltage vector V4Base voltage vector V5；
Sector 7: base voltage vector V3Base voltage vector V4Base voltage vector V5Base voltage vector V6；
Sector 8: base voltage vector V3Base voltage vector V4Base voltage vector V5Base voltage vector V6；
Sector 9: base voltage vector V4Base voltage vector V5Base voltage vector V6Base voltage vector V1；
Sector 10: base voltage vector V4Base voltage vector V5Base voltage vector V6Base voltage vector V1；
Sector 11: base voltage vector V5Base voltage vector V6Base voltage vector V1Base voltage vector V2；
Sector 12: base voltage vector V5Base voltage vector V6Base voltage vector V1Base voltage vector V2；
Recording the reference voltage vector V after sector judgmentrefThe sector is any one of the sectors 1 to 12, the sector is marked as a sector Y, and 3 virtual voltage vectors corresponding to the sector Y are respectively marked as a sector virtual voltage vector V according to the sequence of the virtual voltage vectorsx1Sector virtual voltage vector Vx2And sector virtual voltage vector Vx3The 4 basic voltage vectors corresponding to the sector Y are respectively recorded as the sector basic voltage vector V according to the sequence thereofj1Sector base voltage vector Vj2Sector base voltage vector Vj3And sector base voltage vector Vj4；
Step 3, calculating a reference voltage vector VrefAnd the coordinate axis alpha axis in the static coordinate systemAngle theta, reference voltage vector VrefThe corresponding modulation ratio M is calculated as follows:
Figure BDA0002757012990000051
Figure BDA0002757012990000052
wherein, UdcIs the DC bus voltage, | V, of the DC sourcerefI is a reference voltage vector VrefThe amplitude of (d);
step 4, calculating a sector basic voltage vector V corresponding to the sector Yj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj3Time of action T3And sector base voltage vector Vj4Time of action T4；
When the modulation ratio M is less than or equal to 0.7854, the modulation ratio M is a linear modulation region, and the step 4.1 is carried out;
when the modulation ratio M is larger than 0.7854, the method is an overmodulation region and goes to step 4.2;
step 4.1, a linear modulation region when the modulation ratio M is less than or equal to 0.7854;
firstly, calculating a sector virtual voltage vector V in a linear modulation regionx1Time of action TaSector virtual voltage vector Vx2Time of action TbAnd sector virtual voltage vector Vx3Time of action T0The calculation formula is as follows:
Figure BDA0002757012990000061
wherein, TsIs a switching cycle;
in the linear modulation region, when the sector Y is any one of the sectors 1, 3, 5, 7, 9 and 11, the sector basis voltage vector V is setj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure BDA0002757012990000062
when the sector Y is any one of the sectors 2, 4, 6, 8, 10, and 12, the sector basis voltage vector Vj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure BDA0002757012990000071
step 4.2, an overmodulation region when the modulation ratio M is larger than 0.7854;
step 4.21, recording the modulation compensation angle as ar and the compensation circle reference voltage vector as
Figure BDA0002757012990000072
And setting a compensation circle reference voltage vector
Figure BDA0002757012990000073
Volt-second area and reference voltage vector V swept by one rotationrefEqual, the modulation ratio M and the over-modulation compensation angle ar are related as follows:
Figure BDA0002757012990000074
reference voltage vector of order compensation circle
Figure BDA0002757012990000075
With reference voltage vector VrefKeeping consistent, compensating for circular reference voltage vector
Figure BDA0002757012990000076
Amplitude of
Figure BDA0002757012990000077
The calculation is as follows:
Figure BDA0002757012990000078
reference voltage vector for recording compensation circle
Figure BDA0002757012990000079
The projection components of the alpha and beta axes of the static coordinate system are respectively the alpha axis component V of the compensation circle reference voltage vectorα *Compensating the beta-axis component V of the circular reference voltage vectorβ *Calculating and compensating a circular reference voltage vector
Figure BDA00027570129900000710
Corresponding virtual voltage vector V of sector under compensation statex1Time of action Ta *And a sector virtual voltage vector V in a compensation statex2Time of action Tb *And sector virtual voltage vector V in compensation statex3Time of action T0 *The calculation formula is as follows:
Figure BDA00027570129900000711
when T is0 *When the value is more than or equal to 0, the value is a circular arc area of the overmodulation area, and the step 4.22 is carried out;
when T is0 *If the boundary area is less than 0, the boundary area is an overmodulation area, and the step 4.23 is carried out;
step 4.22, in the arc area of the overmodulation region, when the sector Y is sector 1, sector 3, sector 5, sector 7, sector9. Sector base voltage vector V when any one of sectors 11 is selectedj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure BDA0002757012990000081
when the sector Y is any one of the sectors 2, 4, 6, 8, 10, and 12, the sector basis voltage vector Vj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure BDA0002757012990000082
step 4.23, in the boundary area of the overmodulation region, the sector virtual voltage vector Vx1Sector virtual voltage vector Vx2And sector virtual voltage vector Vx3The action time of (2) is changed, and a sector virtual voltage vector V corresponding to the boundary region is setx1Has an action time of Ta **And sector virtual voltage vector V corresponding to the boundary regionx2Has an action time of Tb **And sector virtual voltage vector V corresponding to the boundary regionx3Has an action time of T0 **The calculation formula is as follows:
Figure BDA0002757012990000091
then in the boundary region of the overmodulation region, when the sector Y is sector 1, sector 3, sector 5, sector7. A sector basic voltage vector V when any one of the sectors 9 and 11 is selectedj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure BDA0002757012990000092
when the sector Y is any one of the sectors 2, 4, 6, 8, 10, and 12, the sector basis voltage vector Vj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure BDA0002757012990000093
step 5, in a switching period TsInternal use of 7-segment wave-forming, in particular, sector base voltage vector V corresponding to sector Yj1Sector base voltage vector Vj2Sector base voltage vector Vj3And sector base voltage vector Vj4The wave generation sequence and the conduction time are as follows:
paragraph 1 and paragraph 7: sector base voltage vector Vj1Corresponding switch state combination (S)a、Sb、Sc) Wave generation, conduction time
Figure BDA0002757012990000101
Paragraph 2 and paragraph 6: sector base voltage vector Vj2Corresponding switch state combination (S)a、Sb、Sc) Wave generation, conduction time
Figure BDA0002757012990000102
Paragraph 3 and paragraph 5: sector base voltage vector Vj3Corresponding switch state combination (S)a、Sb、Sc) Wave generation, conduction time
Figure BDA0002757012990000103
Stage 4: sector base voltage vector Vj4Corresponding switch state combination (S)a、Sb、Sc) Wave generation, conduction time t4＝T4；
Namely, the virtual voltage vector pulse width modulation output with overmodulation is realized.
Preferably, the switching state signal S of the a-phase bridge arm of the three-phase two-level voltage source inverter in step 1aB-phase bridge arm switch state signal SbAnd the switch state signal S of the c-phase bridge armcThe specific actions are as follows:
S a1 represents a three-phase two-level voltage type inverter a-phase bridge arm switching tube Sa1Conducting, switching tube Sa2Turning off;
S a0 represents a three-phase two-level voltage type inverter a-phase bridge arm switching tube Sa1Turn-off, switch tube Sa2Conducting;
S b1 represents a b-phase bridge arm switching tube S of a three-phase two-level voltage type inverterb1Conducting, switching tube Sb2Turning off;
Sbb-phase bridge arm switching tube S of three-phase two-level voltage type inverter is represented by 0b1Turn-off, switch tube Sb2Conducting;
S c1 represents a three-phase two-level voltage type inverter c-phase bridge arm switching tube Sc1Conducting, switching tube Sc2Turning off;
Scc-phase bridge arm switching tube S of three-phase two-level voltage type inverter is represented by 0c1Turn-off, switch tube Sc2And conducting.
Preferably, the 9 virtual nodes in step 1The specific calculation formula of the quasi-voltage vector is as follows:
Figure BDA0002757012990000111
Figure BDA0002757012990000112
preferably, the sector judgment in step 2 is as follows: defining the intermediate variables of the judgment sector as a first variable A, a second variable B, a third variable C, a fourth variable D and a fifth variable N, and defining a functional formula F1，
Figure BDA0002757012990000113
Definition function formula F2，
Figure BDA0002757012990000114
Then:
when V isβWhen the value is more than or equal to 0, A is 1,
when V isβWhen < 0, A is 0,
when V isαWhen the value is more than or equal to 0, B is 1,
when V isαIf < 0, B is 0,
when F is present1When the carbon content is more than or equal to 0, C is 1,
when F is present1When less than 0, C is 0,
when F is present2When D is more than or equal to 0, D is 1,
when F is present2When < 0, D is 0,
N＝A+2B+4C+8D，
each value of the fifth variable N corresponds to a sector, which is specifically as follows:
n15 corresponds to sector 1; n-11 corresponds to sector 2; n-3 corresponds to sector 3; n-1 corresponds to sector 4; n-9 corresponds to sector 5; n13 corresponds to sector 6; n-12 corresponds to sector 7; n-8 corresponds to sector 8; n-0 corresponds to sector 9; n-2 corresponds to sector 10; n10 corresponds to sector 11; n-14 corresponds to sector 12.
Compared with the prior art, the invention has the beneficial effects that:
1. compared with the traditional space vector strategy SVPWM, the method has the advantages that the virtual voltage vector synthesized by the non-zero vector is used for participating in modulating the reference voltage vector, so that the amplitude and the third harmonic component of the common-mode voltage output by the inverter are effectively inhibited;
2. compared with the virtual voltage vector method in reference 2, the invention provides a simple and novel 12-sector judgment implementation method, the innovativeness of the virtual voltage vector method is highlighted, the modulation degree of the algorithm is improved to be 0-0.8247 by the overmodulation technology while the output common-mode voltage amplitude and the third harmonic of the inverter are suppressed by the virtual voltage vector without changing the virtual voltage vector, the maximum direct-current voltage utilization rate is improved by 5% compared with the virtual voltage vector method in reference 2, the overmodulation whole process is smooth, the output voltage fundamental wave amplitude is not lost, and the algorithm applicability is enhanced.
Drawings
Fig. 1 is a three-phase two-level voltage type inverter topology involved in the present invention;
FIG. 2 is a flow chart of an over-modulation operation for any one sector in an embodiment of the present invention;
FIG. 3 is a diagram of a virtual voltage vector composition in accordance with an embodiment of the present invention;
FIG. 4 is a diagram illustrating 12-sector determination in an embodiment of the present invention;
FIG. 5 is a graph of modulation ratio M and over-modulation compensation angle ar in an embodiment of the present invention;
fig. 6 is a schematic diagram of a variation of a common-mode voltage amplitude value output by a three-phase two-level voltage-type inverter when a modulation ratio M is 0.7854 and a conventional SVPWM strategy is used for modulation;
fig. 7 shows the common-mode voltage amplitude of the output of the three-phase two-level voltage-type inverter when the modulation ratio M is 0.7854 and the virtual vector strategy is used for modulation;
FIG. 8 shows the common-mode voltage amplitude of the three-phase two-level voltage-type inverter output when the modulation ratio M is 0.8247 and the virtual vector strategy of the overmodulation region is used for modulation
Fig. 9 is a schematic diagram of a common-mode voltage spectrum of an output of a three-phase two-level voltage-type inverter when a modulation ratio M is 0.7854 and a conventional SVPWM strategy is used for modulation;
fig. 10 is a schematic diagram of a common-mode voltage spectrum of an output of a three-phase two-level voltage-type inverter when a modulation ratio M is 0.7854 and a virtual vector strategy is used for modulation;
fig. 11 is a schematic diagram of a common-mode voltage spectrum output by a three-phase two-level voltage-type inverter when a modulation ratio M is 0.8247 and a virtual vector strategy of an overmodulation region is used for modulation;
fig. 12 is a trend chart of the dc voltage utilization rate corresponding to the fundamental amplitude of the line voltage output by the three-phase two-level voltage-type inverter when the modulation ratio M is 0.78 to 0.84 is modulated by using the virtual vector strategy under the condition that the parameters in the experiment are accurate;
fig. 13 is a graph showing the trend of the variation of the variable N in the sector judgment measured in the experiment.
Detailed Description
The following describes a virtual vector overmodulation strategy for inverter 12 sectors according to the present invention in detail with reference to the accompanying drawings and embodiments.
FIG. 1 is a three-phase two-level voltage type inverter topology structure related to the present invention, and it can be seen from the figure that the three-phase two-level voltage type inverter topology structure related to the present strategy includes a DC source E, a three-phase two-level voltage type inverter, a motor three-phase stator winding, and a capacitor C1And a capacitor C2. In the figure, VSI is a three-phase two-level voltage type inverter, and IM is a three-phase stator winding of the motor. The capacitor C1And a capacitor C2A capacitor C connected between the positive DC bus P and the negative DC bus N of the DC source E1Capacitor C2Is denoted as point o.
In the three-phase bridge arm of the three-phase two-level voltage type inverter, each phase of bridge arm comprises 2 switching tubes with anti-parallel diodes, namely the three-phase two-level voltage type inverter comprises 6 switching tubes with anti-parallel diodes in total, and the 6 switching tubes are respectively marked as switching tubes Sa1Switch tube Sa2Switch tube Sb1Switch tube Sb2Switch tube Sc1Switch tube Sc2. The three-phase bridge arms of the three-phase two-level voltage type inverter are connected in parallel between a direct current positive bus P and a direct current negative bus N, namely a switch tube Sa1Switch tube Sb1Switch tube Sc1The collectors are connected in parallel and then are connected with a direct current positive bus P and a switching tube Sa2Switch tube Sb2Switch tube Sc2The emitting electrodes are connected in parallel and then connected with a direct current negative bus N. In the three-phase arm of a three-phase two-level voltage type inverter, a switching tube Sa1And a switching tube Sa2Series, switch tube Sb1And a switching tube Sb2Series, switch tube Sc1And a switching tube Sc2In series, the connection points are designated as point a, point b, and point c, respectively.
The three-phase stator winding of the motor comprises an A-phase winding, a B-phase winding and a C-phase winding, wherein a left port connecting point a of the A-phase winding, a left port connecting point B of the B-phase winding, a left port connecting point C of the C-phase winding, and right ports of the A-phase winding, the B-phase winding and the C-phase winding are connected together, and the connecting point is marked as a point n.
The invention comprises the following steps:
step 1, setting a switch state, a basic voltage vector and a virtual voltage vector.
Recording the switch state signal of a-phase bridge arm of the three-phase two-level voltage type inverter as a switch state signal SaThe switching state signal of the b-phase bridge arm of the three-phase two-level voltage type inverter is a switching state signal SbThe switching state signal of the c-phase bridge arm of the three-phase two-level voltage type inverter is a switching state signal Sc(ii) a Switch state signal Sa、Sb、ScEqual to 0 or 1.
Obtaining 6 basic voltage vectors according to the switching states of three-phase bridge arms of the three-phase two-level voltage type inverter, and respectively recording the basic voltage vectors as basic voltage vectors V1Base voltage vector V2Base voltage vector V3Base voltage vector V4Base voltage vector V5And a base voltage vector V 66 switching state combinations (S) corresponding to the basic voltage vectorsa、Sb、Sc) The specific states of (a) are as follows:
base voltage vector V1The corresponding switch state combination is (100);
base voltage vector V2The corresponding switch state combination is (110);
base voltage vector V3The corresponding switch state combination is (010);
base voltage vector V4The corresponding switch state combination is (011);
base voltage vector V5The corresponding switch state combination is (001);
base voltage vector V6The corresponding switch state combination is (101).
In an embodiment of the invention, the switch states are combined (S)a、Sb、Sc) The specific actions are as follows:
S a1 represents a three-phase two-level voltage type inverter a-phase bridge arm switching tube Sa1Conducting, switching tube Sa2Turning off;
S a0 represents a three-phase two-level voltage type inverter a-phase bridge arm switching tube Sa1Turn-off, switch tube Sa2Conducting;
S b1 represents a b-phase bridge arm switching tube S of a three-phase two-level voltage type inverterb1Conducting, switching tube Sb2Turning off;
Sbb-phase bridge arm switching tube S of three-phase two-level voltage type inverter is represented by 0b1Turn-off, switch tube Sb2Conducting;
S c1 represents a three-phase two-level voltage type inverter c-phase bridge arm switching tube Sc1Conducting, switching tube Sc2Turning off;
Scc-phase bridge arm switching tube S of three-phase two-level voltage type inverter is represented by 0c1Turn-off, switch tube Sc2And conducting.
The 6 base voltage vectors are used to construct the following 9 virtual voltage vectors: virtual voltage vector V12Virtual voltage vector V23Virtual voltage vector V34Virtual voltage vector V45Virtual voltage vector V56Virtual voltage vector V61Virtual voltage vector V14Virtual voltage vector V25And virtual voltage vector V36。
The specific calculation formula of the 9 virtual voltage vectors is as follows：
Figure BDA0002757012990000141
Figure BDA0002757012990000142
And step 2, judging the sector.
On the α - β axis stationary coordinate system, 12 sectors of 30 ° are divided counterclockwise from the first quadrant with the α axis as a starting point, and the sectors are named as sector 1 to sector 12 in such a manner that the numbers increase in the counterclockwise direction.
Setting a reference voltage vector to be modulated of a three-phase two-level voltage type inverter as VrefReference voltage vector VrefThe projection components of the coordinate axes alpha and beta in the static coordinate system are respectively marked as the components V of the reference voltage vector alphaαAnd a reference voltage vector beta axis component VβFrom the reference voltage vector α -axis component VαAnd a reference voltage vector beta axis component VβCarry out a reference voltage vector VrefAnd judging the located sector.
Defining the intermediate variables of the judgment sector as a first variable A, a second variable B, a third variable C, a fourth variable D and a fifth variable N, and defining a functional formula F1，
Figure BDA0002757012990000151
Definition function formula F2，
Figure BDA0002757012990000152
Then:
when V isβWhen the value is more than or equal to 0, A is 1,
when V isβWhen < 0, A is 0,
when V isαWhen the value is more than or equal to 0, B is 1,
when V isαIf < 0, B is 0,
when F is present1When the carbon content is more than or equal to 0, C is 1,
when F is present1When less than 0, C is 0,
when F is present2When D is more than or equal to 0, D is 1,
when F is present2When < 0, D is 0,
N＝A+2B+4C+8D，
each value of the fifth variable N corresponds to a sector, which is specifically as follows:
n15 corresponds to sector 1; n-11 corresponds to sector 2; n-3 corresponds to sector 3; n-1 corresponds to sector 4; n-9 corresponds to sector 5; n13 corresponds to sector 6; n-12 corresponds to sector 7; n-8 corresponds to sector 8; n-0 corresponds to sector 9; n-2 corresponds to sector 10; n10 corresponds to sector 11; n-14 corresponds to sector 12.
The corresponding relation between different values of the fifth variable N and the sectors is shown in the following table:
N 15 11 3 1 9 13 12 8 0 2 10 14
sector area 1 2 3 4 5 6 7 8 9 10 11 12
Fig. 3 is a virtual voltage vector synthesis diagram in an embodiment of the present invention, and fig. 4 is a diagram illustrating 12-sector determination in an embodiment of the present invention.
Of the 12 sectors, each sector uses 3 virtual voltage vectors vs. a reference voltage vector VrefSynthesizing, wherein 3 virtual voltage vectors relate to 4 basic voltage vectors;
the 3 virtual voltage vectors involved in each of the 12 sectors and the ordering are as follows:
sector 1: virtual voltage vector V61Virtual voltage vector V12Virtual voltage vector V36；
Sector 2: virtual voltage vector V12Virtual voltage vector V23Virtual voltage vector V36；
Sector 3: virtual voltage vector V12Virtual voltage vector V23Virtual voltage vector V14；
Sector 4: virtual voltage vector V23Virtual voltage vector V34Virtual voltage vector V14；
Sector 5: virtual voltage vector V23Virtual voltage vector V34Virtual voltage vector V25；
Sector 6: virtual voltage vector V34Virtual voltage vector V45Virtual voltage vector V25；
Sector 7: virtual voltage vector V34Virtual voltage vector V45Virtual voltage vector V36；
Sector 8: virtual voltage vector V45Virtual voltage vector V56Virtual voltage vector V36：
Sector 9: virtual voltage vector V45Virtual voltage vector V56Virtual voltage vector V14；
Sector 10: virtual voltage vector V56Virtual voltage vector V61Virtual voltage vector V14；
Sector 11: virtual voltage vector V56Virtual voltage vector V61Virtual voltage vector V25；
Sector 12: virtual voltage vector V61Virtual voltage vector V12Virtual voltage vector V25。
The 4 basic voltage vectors involved in each of the 12 sectors and the ordering are as follows:
sector 1: base voltage vector V6Base voltage vector V1Base voltage vector V2Base voltage vector V3；
Sector 2: base voltage vector V6Base voltage vector V1Base voltage vector V2Base voltage vector V3；
Sector 3: base voltage vector V1Base voltage vector V2Base voltage vector V3Base voltage vector V4；
Sector 4: base voltage vector V1Base voltage vector V2Base voltage vector V3Base voltage vector V4；
Sector 5: base voltage vector V2Base voltage vector V3Base voltage vector V4Base voltage vector V5；
Sector 6: base voltage vector V2Base voltage vector V3Base voltage vector V4Base voltage vector V5；
Sector 7: base voltage vector V3Base voltage vector V4Base voltage vector V5Base voltage vector V6；
Sector 8: base voltage vector V3Base voltage vector V4Base voltage vector V5Base voltage vector V6；
Sector 9: base voltage vector V4Base voltage vector V5Base voltage vector V6Base voltage vector V1；
Sector 10: base voltage vector V4Base voltage vector V5Base voltage vector V6Base voltage vector V1；
Sector 11: base voltage vector V5Base voltage vector V6Base voltage vector V1Base voltage vector V2；
Sector 12: base voltage vector V5Base voltage vector V6Base voltage vector V1Base voltage vector V2。
Recording the reference voltage vector V after sector judgmentrefThe sector is any one of the sectors 1 to 12, the sector is marked as a sector Y, and 3 virtual voltage vectors corresponding to the sector Y are respectively marked as a sector virtual voltage vector V according to the sequence of the virtual voltage vectorsx1Sector virtual voltage vector Vx2And sector virtual voltage vector Vx3The 4 basic voltage vectors corresponding to the sector Y are respectively recorded as the sector basic voltage vector V according to the sequence thereofj1Sector base voltage vector Vj2Sector base voltage vector Vj3And sector base voltage vector Vj4。
Fig. 2 is a flow chart of overmodulation operation for any sector according to an embodiment of the present invention, corresponding to steps 3-5.
Step 3, calculating a reference voltage vector VrefAn included angle theta between the reference voltage vector and a coordinate axis alpha axis in a static coordinate system and a reference voltage vector VrefThe corresponding modulation ratio M is calculated as follows:
Figure BDA0002757012990000181
Figure BDA0002757012990000182
wherein, UdcIs the DC bus voltage, | V, of the DC sourcerefI is a reference voltage vector VrefThe amplitude of (c).
Step 4, calculating a sector basic voltage vector V corresponding to the sector Yj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj3Time of action T3And sector base voltage vector Vj4Time of action T4。
When the modulation ratio M is less than or equal to 0.7854, the modulation ratio M is a linear modulation region, and the step 4.1 is carried out;
when the modulation ratio M > 0.7854, the process proceeds to step 4.2 for the overmodulation region.
And 4.1, linear modulation region when the modulation ratio M is less than or equal to 0.7854.
Firstly, calculating a sector virtual voltage vector V in a linear modulation regionx1Time of action TaSector virtual voltage vector Vx2Time of action TbAnd sector virtual voltage vector Vx3Time of action T0The calculation formula is as follows:
Figure BDA0002757012990000183
wherein, TsIs a switching cycle.
In the linear modulation region, when the sector Y is any one of the sectors 1, 3, 5, 7, 9 and 11, the sector basis voltage vector V is setj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure BDA0002757012990000191
when the sector Y is any one of the sectors 2, 4, 6, 8, 10, and 12, the sector basis voltage vector Vj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure BDA0002757012990000192
step 4.2, overmodulation region when modulation ratio M > 0.7854.
Step 4.21, recording the modulation compensation angle as ar and the compensation circle reference voltage vector as
Figure BDA0002757012990000193
And setting a compensation circle reference voltage vector
Figure BDA0002757012990000194
Volt-second area and reference voltage vector V swept by one rotationrefEqual, the modulation ratio M and the over-modulation compensation angle ar are related as follows:
Figure BDA0002757012990000195
reference voltage vector of order compensation circle
Figure BDA0002757012990000196
With reference voltage vector VrefKeeping consistent, compensating for circular reference voltage vector
Figure BDA0002757012990000197
Amplitude of
Figure BDA0002757012990000198
The calculation is as follows:
Figure BDA0002757012990000199
reference voltage vector for recording compensation circle
Figure BDA00027570129900001910
The projection components of the alpha and beta axes of the static coordinate system are respectively the alpha axis component V of the compensation circle reference voltage vectorα *Compensating the beta-axis component V of the circular reference voltage vectorβ *Calculating and compensating a circular reference voltage vector
Figure BDA0002757012990000201
Corresponding virtual voltage vector V of sector under compensation statex1Time of action Ta *And a sector virtual voltage vector V in a compensation statex2Time of action Tb *And sector virtual voltage vector V in compensation statex3Time of action T0 *The calculation formula is as follows:
Figure BDA0002757012990000202
when T is0 *When the value is more than or equal to 0, the value is a circular arc area of the overmodulation area, and the step 4.22 is carried out;
when T is0 *If < 0, the boundary region of the overmodulation region is entered in step 4.23.
Fig. 5 shows the relationship between the modulation ratio M and the overmodulation compensation angle ar in an embodiment of the present invention.
Step 4.22, in the arc region of the overmodulation region, when the sector Y is any one of the sectors 1, 3, 5, 7, 9 and 11, the sector basis voltage vector Vj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure BDA0002757012990000203
when the sector Y is any one of the sectors 2, 4, 6, 8, 10, and 12, the sector basis voltage vector Vj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure BDA0002757012990000211
step 4.23, in the boundary area of the overmodulation region, the sector virtual voltage vector Vx1Sector virtual voltage vector Vx2And sector virtual voltage vector Vx3The action time of (2) is changed, and a sector virtual voltage vector V corresponding to the boundary region is setx1Has an action time of Ta **And sector virtual voltage vector V corresponding to the boundary regionx2Has an action time of Tb **And sector virtual voltage vector V corresponding to the boundary regionx3Has an action time of T0 **The calculation formula is as follows:
Figure BDA0002757012990000212
then in the boundary region of the overmodulation region, when the sector Y is any one of the sectors 1, 3, 5, 7, 9 and 11, the sector basis voltage vector Vj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure BDA0002757012990000213
when the sector Y is any one of the sectors 2, 4, 6, 8, 10, and 12, the sector basis voltage vector Vj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure BDA0002757012990000221
step 5, in a switching period TsInternal use of 7-segment wave-forming, in particular, sector base voltage vector V corresponding to sector Yj1Sector base voltage vector Vj2Sector base voltage vector Vj3And sector base voltage vector Vj4The wave generation sequence and the conduction time are as follows:
paragraph 1 and paragraph 7: sector base voltage vector Vj1Corresponding switch state combination (S)a、Sb、Sc) Wave generation and conductionTime
Figure BDA0002757012990000222
Paragraph 2 and paragraph 6: sector base voltage vector Vj2Corresponding switch state combination (S)a、Sb、Sc) Wave generation, conduction time
Figure BDA0002757012990000223
Paragraph 3 and paragraph 5: sector base voltage vector Vj3Corresponding switch state combination (S)a、Sb、Sc) Wave generation, conduction time
Figure BDA0002757012990000224
Stage 4: sector base voltage vector Vj4Corresponding switch state combination (S)a、Sb、Sc) Wave generation, conduction time t4＝T4。
Namely, the virtual voltage vector pulse width modulation output with overmodulation is realized.
Taking sector 1 as an example, in sector 1, Vj1Is a sector base voltage vector V6、Vj2Is a sector base voltage vector V1、Vj3Is a sector base voltage vector V2、Vj4Is a sector base voltage vector V3The combination of the switch state signals corresponding to each switch state signal is as follows: v6(101)、V1(100)、V2(110)、V3(010)。V6(101)、V1(100)、V2(110)、V3(010) The wave generation sequence, the conduction time and the switching tube action are shown in the following table.
Figure BDA0002757012990000231
In order to verify the effectiveness of the invention, the invention was experimentally verified. The DC source voltage of the three-phase two-level voltage type inverter is 580V, and the three-phase two-level voltage type inverterThe main circuit is composed of Mitsubishi intelligent IGBT power module PM100CLA120, and the switching frequency fsThe dead band is set at 3 mus at 9600 Hz. Using a three-phase asynchronous motor as a load, the asynchronous motor parameters: rated power pn3kW, rated phase voltage UN220V, stator resistance Rs1.93 omega, mutual inductance Lm0.19H, stator inductance Ls0.21H, pole pair number P2, operating frequency fe＝50Hz。
Fig. 6 shows the variation of the common-mode voltage amplitude value output by the three-phase two-level voltage-type inverter when the modulation ratio M is 0.7854 and the conventional SVPWM strategy is used for modulation; fig. 7 shows the variation of the common-mode voltage amplitude value output by the three-phase two-level voltage-type inverter when the modulation ratio M is 0.7854 and the virtual vector strategy is used for modulation; fig. 8 shows the change of the common mode voltage amplitude of the output of the three-phase two-level voltage-type inverter when the modulation ratio M is 0.8247 and the virtual vector strategy of the overmodulation region is used for modulation. Fig. 7 and 8 compare with fig. 6, it can be seen that the virtual vector strategy can better suppress the common-mode voltage amplitude output by the three-phase two-level voltage-type inverter than the conventional SVPWM strategy, and fig. 8 compares with fig. 7, it can be seen that the virtual vector strategy still maintains the capability of suppressing the common-mode voltage amplitude when overmodulation occurs.
Fig. 9 shows the variation of the common-mode voltage spectrum output by the three-phase two-level voltage-type inverter when the modulation ratio M is 0.7854 and the conventional SVPWM strategy is used for modulation; fig. 10 shows the variation of the common-mode voltage spectrum output by the three-phase two-level voltage-type inverter when the modulation ratio M is 0.7854 and the virtual vector strategy is used for modulation; fig. 11 shows a change of a common mode voltage spectrum of an output of the three-phase two-level voltage-type inverter when the modulation ratio M is 0.8247 and the three-phase two-level voltage-type inverter is modulated by using a virtual vector strategy of the overmodulation region. Fig. 10 and 11 in comparison with fig. 9 show that the third harmonic in the common-mode voltage spectrum output by the three-phase two-level voltage-type inverter can be better suppressed by using the virtual vector strategy than by using the conventional SVPWM strategy, and fig. 11 in comparison with fig. 10 shows that the virtual vector strategy still maintains the capability of suppressing the third harmonic in the common-mode voltage spectrum when overmodulation occurs.
Fig. 12 is a direct-current voltage utilization rate variation trend diagram corresponding to the amplitude of the fundamental wave of the line voltage output by the three-phase two-level voltage type inverter when the modulation ratio M of the given voltage command is gradually increased to 0.78 and the modulation ratio M is gradually increased to 0.84 in the experiment and the virtual vector strategy is used for modulation. Therefore, the whole overmodulation process is smooth, the fundamental wave of the voltage of the output line is not lost, the modulatable ratio of the virtual vector strategy can be improved to 0.8247, and the utilization rate of the corresponding maximum direct-current voltage is relatively improved by 5%.
In the experiment, sector division was also verified in the following manner.
As can be seen from fig. 13, the value of the fifth variable N varies in the order of 15, 11, 3, 1, 9, 13, 12, 8, 0, 2, 10, 14 within 0.02s of a fundamental wave period, corresponding to the reference voltage vector VrefThe sector 1 to the sector 12 rotate continuously for one circle, and the judgment of the sector 12 is accurate and effective.

Claims (4)

1. A three-phase two-level voltage type inverter topology structure related to a 12-sector virtual vector overmodulation strategy of an inverter comprises a direct current source E, a three-phase two-level voltage type inverter, a motor three-phase stator winding and a capacitor C1And a capacitor C2(ii) a The capacitor C1And a capacitor C2The direct current source E is connected between a direct current positive bus P and a direct current negative bus N after being connected in series; in the three-phase bridge arm of the three-phase two-level voltage type inverter, each phase of bridge arm comprises 2 switching tubes with anti-parallel diodes, namely the three-phase two-level voltage type inverter comprises 6 switching tubes with anti-parallel diodes in total, and the 6 switching tubes are respectively marked as switching tubes Sa1Switch tube Sa2Switch tube Sb1Switch tube Sb2Switch tube Sc1Switch tube Sc2；
Characterized in that said strategy comprises the following steps:
step 1, setting a switch state, a basic voltage vector and a virtual voltage vector;
recording the switch state signal of a-phase bridge arm of the three-phase two-level voltage type inverter as a switch state signal SaThe switching state signal of the b-phase bridge arm of the three-phase two-level voltage type inverter is a switching state signal SbThree-phase two-level voltage type inverter cThe switching state signal of the phase bridge arm is a switching state signal Sc(ii) a Switch state signal Sa、Sb、ScEqual to 0 or 1;
obtaining 6 basic voltage vectors according to the switching states of three-phase bridge arms of the three-phase two-level voltage type inverter, and respectively recording the basic voltage vectors as basic voltage vectors V1Base voltage vector V2Base voltage vector V3Base voltage vector V4Base voltage vector V5And a base voltage vector V66 switching state combinations (S) corresponding to the basic voltage vectorsa、Sb、Sc) The specific states of (a) are as follows:
base voltage vector V1The corresponding switch state combination is (100);
base voltage vector V2The corresponding switch state combination is (110);
base voltage vector V3The corresponding switch state combination is (010);
base voltage vector V4The corresponding switch state combination is (011);
base voltage vector V5The corresponding switch state combination is (001);
base voltage vector V6The corresponding switch state combination is (101);
the 6 base voltage vectors are used to construct the following 9 virtual voltage vectors: virtual voltage vector V12Virtual voltage vector V23Virtual voltage vector V34Virtual voltage vector V45Virtual voltage vector V56Virtual voltage vector V61Virtual voltage vector V14Virtual voltage vector V25And virtual voltage vector V36；
Step 2, judging a sector;
on an alpha-beta axis static coordinate system, taking an alpha axis as a starting point, dividing the alpha axis into 12 sectors of 30 degrees in the anticlockwise direction from a first quadrant, and naming each sector as sector 1-sector 12 in a mode that the number of the sectors increases in the anticlockwise direction;
reference for setting three-phase two-level voltage type inverter to be modulatedVoltage vector of VrefReference voltage vector VrefThe projection components of the coordinate axes alpha and beta in the static coordinate system are respectively marked as the components V of the reference voltage vector alphaαAnd a reference voltage vector beta axis component VβFrom the reference voltage vector α -axis component VαAnd a reference voltage vector beta axis component VβCarry out a reference voltage vector VrefJudging the located sector;
of the 12 sectors, each sector uses 3 virtual voltage vectors vs. a reference voltage vector VrefSynthesizing, wherein 3 virtual voltage vectors relate to 4 basic voltage vectors;
the 3 virtual voltage vectors involved in each of the 12 sectors and the ordering are as follows:
sector 1: virtual voltage vector V61Virtual voltage vector V12Virtual voltage vector V36；
Sector 2: virtual voltage vector V12Virtual voltage vector V23Virtual voltage vector V36；
Sector 3: virtual voltage vector V12Virtual voltage vector V23Virtual voltage vector V14；
Sector 4: virtual voltage vector V23Virtual voltage vector V34Virtual voltage vector V14；
Sector 5: virtual voltage vector V23Virtual voltage vector V34Virtual voltage vector V25；
Sector 6: virtual voltage vector V34Virtual voltage vector V45Virtual voltage vector V25；
Sector 7: virtual voltage vector V34Virtual voltage vector V45Virtual voltage vector V36；
Sector 8: virtual voltage vector V45Virtual voltage vector V56Virtual voltage vector V36：
Sector 9: virtual voltage vector V45Virtual voltage vector V56Virtual voltage vector V14；
Sector 10: virtual voltage vector V56Virtual voltage vector V61Virtual voltage vector V14；
Sector 11: virtual voltage vector V56Virtual voltage vector V61Virtual voltage vector V25；
Sector 12: virtual voltage vector V61Virtual voltage vector V12Virtual voltage vector V25；
The 4 basic voltage vectors involved in each of the 12 sectors and the ordering are as follows:
sector 1: base voltage vector V6Base voltage vector V1Base voltage vector V2Base voltage vector V3；
Sector 2: base voltage vector V6Base voltage vector V1Base voltage vector V2Base voltage vector V3；
Sector 3: base voltage vector V1Base voltage vector V2Base voltage vector V3Base voltage vector V4；
Sector 4: base voltage vector V1Base voltage vector V2Base voltage vector V3Base voltage vector V4；
Sector 5: base voltage vector V2Base voltage vector V3Base voltage vector V4Base voltage vector V5；
Sector 6: base voltage vector V2Base voltage vector V3Base voltage vector V4Base voltage vector V5；
Sector 7: base voltage vector V3Base voltage vector V4Base voltage vector V5Base voltage vector V6；
Sector 8: base voltage vector V3Base voltage vector V4Base voltage vector V5Base voltage vector V6；
Sector 9: basic electricityPressure vector V4Base voltage vector V5Base voltage vector V6Base voltage vector V1；
Sector 10: base voltage vector V4Base voltage vector V5Base voltage vector V6Base voltage vector V1；
Sector 11: base voltage vector V5Base voltage vector V6Base voltage vector V1Base voltage vector V2；
Sector 12: base voltage vector V5Base voltage vector V6Base voltage vector V1Base voltage vector V2；
Recording the reference voltage vector V after sector judgmentrefThe sector is any one of the sectors 1 to 12, the sector is marked as a sector Y, and 3 virtual voltage vectors corresponding to the sector Y are respectively marked as a sector virtual voltage vector V according to the sequence of the virtual voltage vectorsx1Sector virtual voltage vector Vx2And sector virtual voltage vector Vx3The 4 basic voltage vectors corresponding to the sector Y are respectively recorded as the sector basic voltage vector V according to the sequence thereofj1Sector base voltage vector Vj2Sector base voltage vector Vj3And sector base voltage vector Vj4；
Step 3, calculating a reference voltage vector VrefAn included angle theta between the reference voltage vector and a coordinate axis alpha axis in a static coordinate system and a reference voltage vector VrefThe corresponding modulation ratio M is calculated as follows:
Figure FDA0002757012980000041
Figure FDA0002757012980000042
wherein, UdcIs the DC bus voltage, | V, of the DC sourcerefI is a reference voltage vector VrefOfA value;
step 4, calculating a sector basic voltage vector V corresponding to the sector Yj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj3Time of action T3And sector base voltage vector Vj4Time of action T4；
When the modulation ratio M is less than or equal to 0.7854, the modulation ratio M is a linear modulation region, and the step 4.1 is carried out;
when the modulation ratio M is larger than 0.7854, the method is an overmodulation region and goes to step 4.2;
step 4.1, a linear modulation region when the modulation ratio M is less than or equal to 0.7854;
firstly, calculating a sector virtual voltage vector V in a linear modulation regionx1Time of action TaSector virtual voltage vector Vx2Time of action TbAnd sector virtual voltage vector Vx3Time of action T0The calculation formula is as follows:
Figure FDA0002757012980000043
wherein, TsIs a switching cycle;
in the linear modulation region, when the sector Y is any one of the sectors 1, 3, 5, 7, 9 and 11, the sector basis voltage vector V is setj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure FDA0002757012980000051
when the sector Y is any one of the sectors 2, 4, 6, 8, 10 and 12, the sector basis voltage vectorVj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure FDA0002757012980000052
step 4.2, an overmodulation region when the modulation ratio M is larger than 0.7854;
step 4.21, recording the modulation compensation angle as ar and the compensation circle reference voltage vector as
Figure FDA0002757012980000053
And setting a compensation circle reference voltage vector
Figure FDA0002757012980000054
Volt-second area and reference voltage vector V swept by one rotationrefEqual, the modulation ratio M and the over-modulation compensation angle ar are related as follows:
Figure FDA0002757012980000055
reference voltage vector of order compensation circle
Figure FDA0002757012980000056
With reference voltage vector VrefKeeping consistent, compensating for circular reference voltage vector
Figure FDA0002757012980000057
Amplitude of
Figure FDA0002757012980000058
The calculation is as follows:
Figure FDA0002757012980000059
reference voltage vector for recording compensation circle
Figure FDA00027570129800000510
The projection components of the alpha and beta axes of the static coordinate system are respectively the alpha axis component V of the compensation circle reference voltage vectorα *Compensating the beta-axis component V of the circular reference voltage vectorβ *Calculating and compensating a circular reference voltage vector
Figure FDA0002757012980000061
Corresponding virtual voltage vector V of sector under compensation statex1Time of action Ta *And a sector virtual voltage vector V in a compensation statex2Time of action Tb *And sector virtual voltage vector V in compensation statex3Time of action T0 *The calculation formula is as follows:
Figure FDA0002757012980000062
when T is0 *When the value is more than or equal to 0, the value is a circular arc area of the overmodulation area, and the step 4.22 is carried out;
when T is0 *If the boundary area is less than 0, the boundary area is an overmodulation area, and the step 4.23 is carried out;
step 4.22, in the arc region of the overmodulation region, when the sector Y is any one of the sectors 1, 3, 5, 7, 9 and 11, the sector basis voltage vector Vj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure FDA0002757012980000063
when the sector Y is any one of the sectors 2, 4, 6, 8, 10, and 12, the sector basis voltage vector Vj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure FDA0002757012980000071
step 4.23, in the boundary area of the overmodulation region, the sector virtual voltage vector Vx1Sector virtual voltage vector Vx2And sector virtual voltage vector Vx3The action time of (2) is changed, and a sector virtual voltage vector V corresponding to the boundary region is setx1Has an action time of Ta **And sector virtual voltage vector V corresponding to the boundary regionx2Has an action time of Tb **And sector virtual voltage vector V corresponding to the boundary regionx3Has an action time of T0 **The calculation formula is as follows:
Figure FDA0002757012980000072
then in the boundary region of the overmodulation region, when the sector Y is any one of the sectors 1, 3, 5, 7, 9 and 11, the sector basis voltage vector Vj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure FDA0002757012980000073
when the sector Y is any one of the sectors 2, 4, 6, 8, 10, and 12, the sector basis voltage vector Vj1Time of action T1Sector base voltage vector Vj2Time of action T2Sector base voltage vector Vj2Time of action T3And sector base voltage vector Vj4Time of action T4Respectively as follows:
Figure FDA0002757012980000081
step 5, in a switching period TsInternal use of 7-segment wave-forming, in particular, sector base voltage vector V corresponding to sector Yj1Sector base voltage vector Vj2Sector base voltage vector Vj3And sector base voltage vector Vj4The wave generation sequence and the conduction time are as follows:
paragraph 1 and paragraph 7: sector base voltage vector Vj1Corresponding switch state combination (S)a、Sb、Sc) Wave generation, conduction time
Figure FDA0002757012980000082
Paragraph 2 and paragraph 6: sector base voltage vector Vj2Corresponding switch state combination (S)a、Sb、Sc) Wave generation, conduction time
Figure FDA0002757012980000083
Paragraph 3 and paragraph 5: sector base voltage vector Vj3Corresponding switch state combination (S)a、Sb、Sc) Wave generation, conduction time
Figure FDA0002757012980000084
Stage 4: sector base voltage vector Vj4Corresponding switch state combination (S)a、Sb、Sc) Wave generation, conduction time t4＝T4；
Namely, the virtual voltage vector pulse width modulation output with overmodulation is realized.
2. The strategy for overmodulation by a virtual vector in an inverter 12 sector according to claim 1, wherein the switching state signal S of the a-phase bridge arm of the three-phase two-level voltage-type inverter in step 1aB-phase bridge arm switch state signal SbAnd the switch state signal S of the c-phase bridge armcThe specific actions are as follows:
Sa1 represents a three-phase two-level voltage type inverter a-phase bridge arm switching tube Sa1Conducting, switching tube Sa2Turning off;
Sa0 represents a three-phase two-level voltage type inverter a-phase bridge arm switching tube Sa1Turn-off, switch tube Sa2Conducting;
Sb1 represents a b-phase bridge arm switching tube S of a three-phase two-level voltage type inverterb1Conducting, switching tube Sb2Turning off;
Sbb-phase bridge arm switching tube S of three-phase two-level voltage type inverter is represented by 0b1Turn-off, switch tube Sb2Conducting;
Sc1 represents a three-phase two-level voltage type inverter c-phase bridge arm switching tube Sc1Conducting, switching tube Sc2Turning off;
Scc-phase bridge arm switching tube S of three-phase two-level voltage type inverter is represented by 0c1Turn-off, switch tube Sc2And conducting.
3. The strategy for overmodulation of a virtual vector of a 12-sector inverter according to claim 1, wherein the 9 virtual voltage vectors in step 1 are calculated by the following formula:
Figure FDA0002757012980000091
Figure FDA0002757012980000092
Figure FDA0002757012980000093
4. the strategy for overmodulation by a virtual vector of an inverter 12 sector according to claim 1, wherein the sector judgment in step 2 is as follows: defining the intermediate variables of the judgment sector as a first variable A, a second variable B, a third variable C, a fourth variable D and a fifth variable N, and defining a functional formula F1，
Figure FDA0002757012980000094
Definition function formula F2，
Figure FDA0002757012980000095
Then:
when V isβWhen the value is more than or equal to 0, A is 1,
when V isβWhen < 0, A is 0,
when V isαWhen the value is more than or equal to 0, B is 1,
when V isαIf < 0, B is 0,
when F is present1When the carbon content is more than or equal to 0, C is 1,
when F is present1When less than 0, C is 0,
when F is present2When D is more than or equal to 0, D is 1,
when F is present2When < 0, D is 0,
N＝A+2B+4C+8D，
each value of the fifth variable N corresponds to a sector, which is specifically as follows:
n15 corresponds to sector 1; n-11 corresponds to sector 2; n-3 corresponds to sector 3; n-1 corresponds to sector 4; n-9 corresponds to sector 5; n13 corresponds to sector 6; n-12 corresponds to sector 7; n-8 corresponds to sector 8; n-0 corresponds to sector 9; n-2 corresponds to sector 10; n10 corresponds to sector 11; n-14 corresponds to sector 12.
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