CN105450059A - Modulation method for suppressing leakage current of two-H-bridge cascaded inverter - Google Patents
Modulation method for suppressing leakage current of two-H-bridge cascaded inverter Download PDFInfo
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- CN105450059A CN105450059A CN201510975756.2A CN201510975756A CN105450059A CN 105450059 A CN105450059 A CN 105450059A CN 201510975756 A CN201510975756 A CN 201510975756A CN 105450059 A CN105450059 A CN 105450059A
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Classifications
-
- 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
-
- H02J3/383—
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0038—Circuits or arrangements for suppressing, e.g. by masking incorrect turn-on or turn-off signals, e.g. due to current spikes in current mode control
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
- H02M1/007—Plural converter units in cascade
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
- H02M1/123—Suppression of common mode voltage or current
-
- 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
- H02M7/493—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 the static converters being arranged for operation in parallel
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
The invention discloses a modulation method for suppressing leakage current of a two-H-bridge cascaded inverter. The method comprises the following steps of calculating total parasitic capacitor voltage v<Nto> value of the two-H-bridge cascaded inverter at each switch-on state; selecting all switch-on states when the total parasitic capacitor voltage v<Nto) is -v<dc>; forming a combination of two switch-on states according to requirements of maximum level output, switch stress reduction and output power balance of a module; and comparing a modulation wave with a triangle carrier wave which is laminated by two same or opposite phases, and generating pulse width modulation (PWM) signals conforming to the above switch-on state combination, and allocating the PWM signals to corresponding pins. By the scheme, extra hardware cost is not needed, leakage current flowing into a power grid can be eliminated, and meanwhile, the leakage current of a single module is suppressed; and the method only requires two carrier waves to compare, the computation of a processor is reduced, and the implementation mode is simple.
Description
Technical field
The present invention relates to a kind of modulator approach of single-phase two H bridge cascaded inverters, especially can suppress the modulator approach of non-isolation type two H bridge cascade grid-connected photovoltaic inverter leakage current; It is applicable to parallel network power generation field.
Background technology
For ensureing use safety, VDE4105 standard has strict restriction to photovoltaic (Photovoltaic, PV) grid-connected system common mode current (leakage current).Adopt net side power frequency isolation transformer can realize electrical isolation, the suppression leakage current of PV and electrical network, but Industrial Frequency Transformer volume is large, Heavy Weight, cost are high, system effectiveness is low.Realize the electrical isolation of PV and electrical network according to high frequency transformer, system bulk, weight and cost can be reduced, but power conversion is divided into several grades, and system effectiveness does not have clear improvement.And the conversion efficiency of combining inverter and the generating efficiency of photovoltaic generating system closely related.Therefore, efficiency is high, volume is little, lightweight and that cost is low non-isolated grid-connected inverter has a clear superiority in.But save transformer and make there has been electrical connection between photovoltaic battery panel and electrical network, leakage current may significantly increase, and bring conduction and radiated interference, increase grid-connected current harmonic wave and loss, even jeopardize equipment and personal security.Therefore suppress the leakage current of non-isolated grid-connected inverter to become one of study hotspot.
Existing non-isolation type single-phase photovoltaic grid-connected inverter is successfully applied to commercial sources, as the SunnyMiniCentral series photovoltaic inverter of SMA company at present.But these structures are all the modified model topologys based on single H bridge, are only applicable to small-power occasion.And photovoltaic DC-to-AC converter of future generation needs to reach higher power grade and efficiency, therefore multi-electrical level inverter becomes main study subject.Cascaded H-bridges multi-electrical level inverter has the advantages that modularization is easily expanded, cost is low and output voltage quality is high, and its DC side can be independently-powered by photovoltaic battery panel, make its independent MPPT maximum power point tracking (MPPT) control to become possibility, thus cascaded H-bridges structure becomes the photovoltaic DC-to-AC converter structure of most prospect.Meanwhile, the leakage current of cascaded H-bridges photovoltaic combining inverter also becomes a major issue.
The drain current suppressing of current cascaded H-bridges photovoltaic combining inverter has some achievements, as be entitled as " Analysisandsuppressionofleakagecurrentincascaded-multile vel-inverterbasedPVsystems; " Y.ZhouandH.Li, " IEEETrans.PowerElectron. ", 2014,29 (10), 5265 – 5277 (" cascade connection multi-level photovoltaic inverter leakage current analysis and inhibition ", " IEEE journal-power electronics periodical ", the 29th volume the 10th phase 5265 – 5277 pages in 2014) article; This article proposes two kinds of drain current suppressing schemes, is to adopt different passive filters respectively in DC side and AC, but the program has the following disadvantages:
1) passive filter is primarily of inductance and electric capacity composition, applies volume, weight and the cost that can increase inverter in circuit, reduces the energy conversion efficiency of inverter simultaneously;
2) leakage current harmonic wave scope is comparatively wide, and by such environmental effects, makes filter parameter design process comparatively complicated;
3) cascaded H-bridges inverter actual operating frequency is lower, and the major harmonic frequency of its leakage current is also lower, causes the drain current suppressing effect of filter unsatisfactory.
Be entitled as " HybridMulticarrierModulationtoReduceLeakageCurrentinaTra nsformerlessCascadedMultilevelInverterforPhotovoltaicSys tems ", RajasekarSelvamuthukumaran, AbhishekGarg, andRajeshGupta, " IEEETransactionsonPowerElectron ", 2015, 30 (4), 1779-1783 (" reducing the hybrid modulation stratgy of non-isolation type photovoltaic inverter leakage current ", " IEEE journal-power electronics periodical ", 30th volume the 4th phase 1779-1783 page in 2015) article, this article proposes a kind of modulation strategy of the two H bridge cascaded inverters based on two carrier waves realizations, and the deficiency of the method is as follows:
1) this modulator approach can not suppress the leakage current flowing into electrical network, cannot improve grid-connected current quality;
2) the method use the stacked carrier wave of two homophases, but need phase shift 180 ° every half power frequency period carrier wave, this adds hardware implementing difficulty undoubtedly.
As can be seen here, prior art can not increase extra cost and under not affecting grid-connected current quality, solve the leakage problem of bridge cascaded H-bridges inverter preferably.
Summary of the invention
The technical problem to be solved in the present invention is for overcoming problems of the prior art, propose a kind ofly not need extra hardware, can eliminate and flow into the leakage current of electrical network, and suppress single module leakage current, and the modulator approach of the simple suppression two H bridge cascaded inverter leakage current of implementation.
In order to complete object of the present invention, the present invention proposes the modulator approach of a kind of suppression two H bridge cascaded inverter leakage currents, comprising switching sequence and selecting; The key step of this modulator approach is as follows:
Step 1, if two module direct voltages of two H bridge cascaded inverters are identical, and is designated as v
dc, calculate all 16 kinds of on off state (S of two H bridge cascaded inverters
a1s
b1s
a2s
b2) output voltage U
o, module 1 parasitic capacitor voltage v
n1O, module 2 parasitic capacitor voltage v
n2Oand total parasitic capacitor voltage v
ntOvalue,
U
O＝v
dc(S
a1-S
b1+S
a2-S
b2)，
v
N1O＝-0.5v
dc(S
a1+S
b1-S
a2+S
b2)，
v
N2O＝-0.5v
dc(S
a1-S
b1+S
a2+S
b2)，
v
NtO＝v
N1O+v
N2O；
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2meet for the switch function of brachium pontis that is connected with total output in module 2:
Step 2, according to the result that step 1 calculates, selects total parasitic capacitor voltage v
ntOfor-v
dcall on off states, wherein v
dcfor each module direct voltage;
Step 3, according to the result that step 2 is selected, according to exporting maximum level, reducing the requirement of switch stress and balance module power output, the following two kinds of Switch State Combination in Power Systems of composition:
The first Switch State Combination in Power Systems: 1010-1000-1100-0011-0001-0101;
The first Switch State Combination in Power Systems: 1010-1110-1100-0011-0111-0101;
Step 4, to step 3 obtain two kinds of Switch State Combination in Power Systems, respectively select following methods obtain pwm signal:
The first Switch State Combination in Power Systems, implementation method is that modulating wave compares with two stacked triangular carriers and obtains pwm signal;
The second Switch State Combination in Power Systems, implementation method is that modulating wave compares with two stacked triangular carriers and obtains pwm signal.
Preferably, the method for Switch State Combination in Power Systems described in step 3 is:
At the positive half cycle of modulating wave, selector switch state 1100 exports 0 level, selector switch state 1000 or 1110 output+v
dclevel, selector switch state 1010 exports+2v
dclevel;
At modulating wave negative half period, selector switch state 0011 exports 0 level, selector switch state 0001 or 0111 output-v
dclevel, selector switch state 0101 exports-2v
dclevel;
On off state 0011 and 1100 switch at modulating wave zero crossing.
Preferably, the pwm signal producing method of the first Switch State Combination in Power Systems described in step 4 is:
(1) as modulating wave V
refbe in positive half period, i.e. V
ref>=0, then S
a1=1, S
b2=0; S
b1by modulating wave and carrier wave V
c2relatively obtain, if V
ref>V
c2, S
b1=0, otherwise S
b1=1; S
a2by modulating wave and carrier wave V
c1relatively obtain, if V
ref>V
c1, S
a2=1, otherwise S
a2=0;
(2) as modulating wave V
refbe in negative half-cycle, i.e. V
ref<0, then S
a1=0, S
b2=1; In order to make carrier wave and modulating wave compare, modulating wave being added 1 and obtaining revised modulating wave V
ref *, i.e. V
ref *=V
ref+ 1; S
b1by modulating wave V
ref *with carrier wave V
c2relatively obtain, if V
ref *>V
c2, S
b1=0, otherwise S
b1=1; S
a2by modulating wave V
ref *with carrier wave V
c1relatively obtain, if V
ref *>V
c1, S
a2=1, otherwise S
a2=0;
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2for the switch function of brachium pontis be connected with total output in module 2, V
c1, V
c2be two stacked triangular carriers, and V
c1>=V
c2>=0.
Preferably, the pwm signal producing method of the Switch State Combination in Power Systems of the second described in step 4 is,
(1) as modulating wave V
refbe in positive half period, i.e. V
ref>=0, then S
a1=1, S
b2=0; S
b1by modulating wave and carrier wave V
c1relatively obtain, if V
ref>V
c1, S
b1=0, otherwise S
b1=1; S
a2by modulating wave and carrier wave V
c2relatively obtain, if V
ref>V
c2, S
a2=1, otherwise S
a2=0;
(2) as modulating wave V
refbe in negative half-cycle, i.e. V
ref<0, then S
a1=0, S
b2=1; In order to make carrier wave and modulating wave compare, modulating wave being added 1 and obtaining revised modulating wave V
ref *, i.e. V
ref *=V
ref+ 1; S
b1by modulating wave V
ref *with carrier wave V
c1relatively obtain, if V
ref *>V
c1, S
b1=0, otherwise S
b1=1; S
a2by modulating wave V
ref *with carrier wave V
c2relatively obtain, if V
ref *>V
c2, S
a2=1, otherwise S
a2=0;
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2for the switch function of brachium pontis be connected with total output in module 2, V
c1, V
c2be two stacked triangular carriers, and V
c1>=V
c2>=0.
Preferably, stacked triangular carrier described in step 4 is two synchronous stacked triangular carriers.
Preferably, stacked triangular carrier described in step 4 is the stacked triangular carrier of two antiphases.
Relative to prior art, beneficial effect of the present invention is as follows:
1, do not need extra hardware, the volume of inverter, weight and cost can not be increased, the energy conversion efficiency of inverter can not be reduced simultaneously.
2, the leakage current flowing into electrical network can be eliminated, and then improve power network current quality; Single module leakage current can be suppressed simultaneously, reduce system loss and electromagnetic interference.
3, only need two carrier waves, and do not need to carry out phase-shifting carrier wave, just can obtain the pwm signal of all switching tubes, implementation is simple.
Accompanying drawing explanation
Fig. 1 is overview flow chart of the present invention.
Fig. 2 is single-phase two H bridge tandem photovoltaic combining inverter schematic diagrams.
Fig. 3 is that the first switch combination homophase carrier wave realizes schematic diagram.
Fig. 4 is that the first switch combination phase inverted carrier realizes schematic diagram.
Fig. 5 is that the second switch combination homophase carrier wave realizes schematic diagram.
Fig. 6 is that the second switch combination phase inverted carrier realizes schematic diagram.
Embodiment
In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is described in more detail.
The modulator approach of suppression two H bridge cascaded inverter leakage current disclosed by the invention is applied to single-phase non-isolated two H bridge tandem photovoltaic grid-connected system, and systematic schematic diagram as shown in Figure 2.In Fig. 2, module 1 and module 2 are H bridge construction, and the series connection of its AC exports, through two filter inductance L
1and L
2be connected to electrical network E
g.Each module DC side is powered by photovoltaic battery panel, and direct voltage is v
dc.C
pv1and C
pv2be the photovoltaic panel parasitic capacitance of module 1 and module 2 respectively, its both end voltage is respectively v
n1Oand v
n2O.
In two H bridge cascaded inverters, the on off state of each brachium pontis can be expressed as follows by switch function,
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2for the switch function of brachium pontis be connected with total output in module 2.
Two H bridge cascaded inverters always have 16 breaker in middle states, and often kind of on off state can by one group of switch function (S
a1s
b1s
a2s
b2) represent, as 0101,1010 etc.
For two H bridge tandem photovoltaic combining inverters single-phase shown in Fig. 2, the basic step of the modulator approach of suppression two H bridge cascaded inverter leakage current disclosed by the invention is as follows:
See Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 and Fig. 6,
Step 1, if two module direct voltages of two H bridge cascaded inverters are identical, and is designated as v
dc, calculate all 16 kinds of on off state (S of two H bridge cascaded inverters
a1s
b1s
a2s
b2) output voltage U
o, module 1 parasitic capacitor voltage v
n1O, module 2 parasitic capacitor voltage v
n2Oand total parasitic capacitor voltage v
ntOvalue,
U
O＝v
dc(S
a1-S
b1+S
a2-S
b2)，
v
N1O＝-0.5v
dc(S
a1+S
b1-S
a2+S
b2)，
v
N2O＝-0.5v
dc(S
a1-S
b1+S
a2+S
b2)，
v
NtO＝v
N1O+v
N2O；
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2meet for the switch function of brachium pontis that is connected with total output in module 2:
Result of calculation is as shown in table 1
Table 1 on off state and common-mode voltage
Step 2, according to the result that step 1 calculates, selects total parasitic capacitor voltage v
ntOfor-v
dcall on off states, wherein v
dcfor each module direct voltage, selection result is as shown in italics in table 1;
Step 3, according to the result that step 2 is selected, according to exporting maximum level, reducing the requirement of switch stress and balance module power output, the following two kinds of Switch State Combination in Power Systems of composition:
The first Switch State Combination in Power Systems: 1010-1000-1100-0011-0001-0101;
The first Switch State Combination in Power Systems: 1010-1110-1100-0011-0111-0101;
The method of Switch State Combination in Power Systems is:
At the positive half cycle of modulating wave, selector switch state 1100 exports 0 level, selector switch state 1000 or 1110 output+v
dclevel, selector switch state 1010 exports+2v
dclevel;
At modulating wave negative half period, selector switch state 0011 exports 0 level, selector switch state 0001 or 0111 output-v
dclevel, selector switch state 0101 exports-2v
dclevel;
On off state 0011 and 1100 switch at modulating wave zero crossing;
Step 4, to step 3 obtain two kinds of Switch State Combination in Power Systems, respectively select following methods obtain pwm signal:
The first Switch State Combination in Power Systems, its implementation is that modulating wave compares with two stacked triangular carriers and obtains pwm signal, and wherein stacked triangular carrier is the stacked triangular carrier of two same-phases or antiphase, and concrete manner of comparison is as follows:
(1) as modulating wave V
refbe in positive half period, i.e. V
ref>=0, then S
a1=1, S
b2=0; S
b1by modulating wave and carrier wave V
c2relatively obtain, if V
ref>V
c2, S
b1=0, otherwise S
b1=1; S
a2by modulating wave and carrier wave V
c1relatively obtain, if V
ref>V
c1, S
a2=1, otherwise S
a2=0;
(2) as modulating wave V
refbe in negative half-cycle, i.e. V
ref<0, then S
a1=0, S
b2=1; In order to make carrier wave and modulating wave compare, modulating wave being added 1 and obtaining revised modulating wave V
ref *, i.e. V
ref *=V
ref+ 1; S
b1by modulating wave V
ref *with carrier wave V
c2relatively obtain, if V
ref *>V
c2, S
b1=0, otherwise S
b1=1; S
a2by modulating wave V
ref *with carrier wave V
c1relatively obtain, if V
ref *>V
c1, S
a2=1, otherwise S
a2=0;
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2for the switch function of brachium pontis be connected with total output in module 2, V
c1, V
c2be two stacked triangular carriers, and V
c1>=V
c2>=0.
The second Switch State Combination in Power Systems, its implementation is that modulating wave compares with two stacked triangular carriers and obtains pwm signal, and wherein stacked triangular carrier is the stacked triangular carrier of two same-phases or antiphase.Specific implementation is as follows:
(1) as modulating wave V
refbe in positive half period, i.e. V
ref>=0, then S
a1=1, S
b2=0; S
b1by modulating wave and carrier wave V
c1relatively obtain, if V
ref>V
c1, S
b1=0, otherwise S
b1=1; S
a2by modulating wave and carrier wave V
c2relatively obtain, if V
ref>V
c2, S
a2=1, otherwise S
a2=0;
(2) as modulating wave V
refbe in negative half-cycle, i.e. V
ref<0, then S
a1=0, S
b2=1; In order to make carrier wave and modulating wave compare, modulating wave being added 1 and obtaining revised modulating wave V
ref *, i.e. V
ref *=V
ref+ 1; S
b1by modulating wave V
ref *with carrier wave V
c1relatively obtain, if V
ref *>V
c1, S
b1=0, otherwise S
b1=1; S
a2by modulating wave V
ref *with carrier wave V
c2relatively obtain, if V
ref *>V
c2, S
a2=1, otherwise S
a2=0;
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2for the switch function of brachium pontis be connected with total output in module 2, V
c1, V
c2be two stacked triangular carriers, and V
c1>=V
c2>=0.
Below in conjunction with specific embodiment, the present invention is described in more detail.
Embodiment 1
Step 1, if two module direct voltages of two H bridge cascaded inverters are identical, and is designated as v
dc, calculate all 16 kinds of on off state (S of two H bridge cascaded inverters
a1s
b1s
a2s
b2) output voltage U
o, module 1 parasitic capacitor voltage v
n1O, module 2 parasitic capacitor voltage v
n2Oand total parasitic capacitor voltage v
ntOvalue,
U
O＝v
dc(S
a1-S
b1+S
a2-S
b2)，
v
N1O＝-0.5v
dc(S
a1+S
b1-S
a2+S
b2)，
v
N2O＝-0.5v
dc(S
a1-S
b1+S
a2+S
b2)，
v
NtO＝v
N1O+v
N2O；
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2meet for the switch function of brachium pontis that is connected with total output in module 2:
Result of calculation is as shown in table 1;
Step 2, according to the result that step 1 calculates, selects total parasitic capacitor voltage v
ntOfor-v
dcall on off states, wherein v
dcfor each module direct voltage, selection result is as shown in italics in table 1;
Step 3, according to the result that step 2 is selected, according to exporting maximum level, reducing the requirement of switch stress and balance module power output, the following two kinds of Switch State Combination in Power Systems of composition:
The first Switch State Combination in Power Systems: 1010-1000-1100-0011-0001-0101;
The first Switch State Combination in Power Systems: 1010-1110-1100-0011-0111-0101;
The method of Switch State Combination in Power Systems is:
At the positive half cycle of modulating wave, selector switch state 1100 exports 0 level, selector switch state 1000 or 1110 output+v
dclevel, selector switch state 1010 exports+2v
dclevel;
At modulating wave negative half period, selector switch state 0011 exports 0 level, selector switch state 0001 or 0111 output-v
dclevel, selector switch state 0101 exports-2v
dclevel;
On off state 0011 and 1100 switch at modulating wave zero crossing;
Step 4, to the first Switch State Combination in Power Systems that step 3 obtains, its implementation is that modulating wave compares with two synchronous stacked triangular carriers and obtains pwm signal, and concrete manner of comparison is as follows:
(1) as modulating wave V
refbe in positive half period, i.e. V
ref>=0, then S
a1=1, S
b2=0; S
b1by modulating wave and carrier wave V
c2relatively obtain, if V
ref>V
c2, S
b1=0, otherwise S
b1=1; S
a2by modulating wave and carrier wave V
c1relatively obtain, if V
ref>V
c1, S
a2=1, otherwise S
a2=0;
(2) as modulating wave V
refbe in negative half-cycle, i.e. V
ref<0, then S
a1=0, S
b2=1; In order to make carrier wave and modulating wave compare, modulating wave being added 1 and obtaining revised modulating wave V
ref *, i.e. V
ref *=V
ref+ 1; S
b1by modulating wave V
ref *with carrier wave V
c2relatively obtain, if V
ref *>V
c2, S
b1=0, otherwise S
b1=1; S
a2by modulating wave V
ref *with carrier wave V
c1relatively obtain, if V
ref *>V
c1, S
a2=1, otherwise S
a2=0;
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2for the switch function of brachium pontis be connected with total output in module 2, V
c1, V
c2be two stacked triangular carriers, and V
c1>=V
c2>=0.
The present embodiment realize schematic diagram as shown in Figure 3, in Fig. 3, T is the modulating wave cycle, and all on off states that visible this manner of comparison produces are all identical with the first Switch State Combination in Power Systems.
Embodiment 2
The present embodiment adopts modulating wave to compare with the stacked triangular carrier of two antiphases, realizes the first switch combination in embodiment 1.Realize schematic diagram as shown in Figure 4, in Fig. 4, T is the modulating wave cycle, and carrier wave manner of comparison is identical with embodiment 1, and all on off states that visible this manner of comparison produces are all identical with the first Switch State Combination in Power Systems.
Embodiment 3
The present embodiment is adopted as modulating wave and compares with two synchronous stacked triangular carriers, and realize the second switch combination in embodiment 1, manner of comparison is:
(1) as modulating wave V
refbe in positive half period, i.e. V
ref>=0, then S
a1=1, S
b2=0; S
b1by modulating wave and carrier wave V
c1relatively obtain, if V
ref>V
c1, S
b1=0, otherwise S
b1=1; S
a2by modulating wave and carrier wave V
c2relatively obtain, if V
ref>V
c2, S
a2=1, otherwise S
a2=0;
(2) as modulating wave V
refbe in negative half-cycle, i.e. V
ref<0, then S
a1=0, S
b2=1; In order to make carrier wave and modulating wave compare, modulating wave being added 1 and obtaining revised modulating wave V
ref *, i.e. V
ref *=V
ref+ 1; S
b1by modulating wave V
ref *with carrier wave V
c1relatively obtain, if V
ref *>V
c1, S
b1=0, otherwise S
b1=1; S
a2by modulating wave V
ref *with carrier wave V
c2relatively obtain, if V
ref *>V
c2, S
a2=1, otherwise S
a2=0;
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2for the switch function of brachium pontis be connected with total output in module 2, V
c1, V
c2be two stacked triangular carriers, and V
c1>=V
c2>=0.
The homophase carrier wave of the second switch combination realizes schematic diagram as shown in Figure 5, and in Fig. 5, T is the modulating wave cycle, and all on off states that visible this manner of comparison produces are all identical with the second Switch State Combination in Power Systems.
Embodiment 4
The present embodiment adopts modulating wave to compare with the stacked triangular carrier of two antiphases, realizes the second switch combination in embodiment 1.Realize schematic diagram as shown in Figure 6, in Fig. 6, T is the modulating wave cycle, and carrier wave manner of comparison is identical with embodiment 3, and all on off states that visible this manner of comparison produces are all identical with the second Switch State Combination in Power Systems.
Finally, produce corresponding drive singal according to the switch function obtained, be dispensed to corresponding switching tube according to the distribution principle of inverter.
Those skilled in the art will readily understand; the foregoing is only preferred embodiment of the present invention; not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.
Claims (6)
1. suppress a modulator approach for two H bridge cascaded inverter leakage currents, comprise switching sequence and select, it is characterized in that, the key step of this modulator approach is as follows:
Step 1, if two module direct voltages of two H bridge cascaded inverters are identical, and is designated as v
dc, calculate all 16 kinds of on off state (S of two H bridge cascaded inverters
a1s
b1s
a2s
b2) output voltage U
o, module 1 parasitic capacitor voltage v
n1O, module 2 parasitic capacitor voltage v
n2Oand total parasitic capacitor voltage v
ntOvalue,
U
O＝v
dc(S
a1-S
b1+S
a2-S
b2)，
v
N1O＝-0.5v
dc(S
a1+S
b1-S
a2+S
b2)，
v
N2O＝-0.5v
dc(S
a1-S
b1+S
a2+S
b2)，
v
NtO＝v
N1O+v
N2O；
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2meet for the switch function of brachium pontis that is connected with total output in module 2:
Step 2, according to the result that step 1 calculates, selects total parasitic capacitor voltage v
ntOfor-v
dcall on off states, wherein v
dcfor each module direct voltage;
Step 3, according to the result that step 2 is selected, according to exporting maximum level, reducing the requirement of switch stress and balance module power output, the following two kinds of Switch State Combination in Power Systems of composition:
The first Switch State Combination in Power Systems: 1010-1000-1100-0011-0001-0101;
The second Switch State Combination in Power Systems: 1010-1110-1100-0011-0111-0101;
Step 4, to step 3 obtain two kinds of Switch State Combination in Power Systems, respectively select following methods obtain pwm signal:
The first Switch State Combination in Power Systems, implementation method is that modulating wave compares with two stacked triangular carriers and obtains pwm signal;
The second Switch State Combination in Power Systems, implementation method is that modulating wave compares with two stacked triangular carriers and obtains pwm signal.
2. the modulator approach of a kind of suppression two H bridge cascaded inverter leakage currents according to right 1, it is characterized in that, the method for Switch State Combination in Power Systems described in step 3 is:
At the positive half cycle of modulating wave, selector switch state 1100 exports 0 level, selector switch state 1000 or 1110 output+v
dclevel, selector switch state 1010 exports+2v
dclevel;
At modulating wave negative half period, selector switch state 0011 exports 0 level, selector switch state 0001 or 0111 output-v
dclevel, selector switch state 0101 exports-2v
dclevel;
On off state 0011 and 1100 switch at modulating wave zero crossing.
3. the modulator approach of a kind of suppression two H bridge cascaded inverter leakage currents according to right 1, it is characterized in that, the pwm signal producing method of the first Switch State Combination in Power Systems described in step 4 is:
(1) as modulating wave V
refbe in positive half period, i.e. V
ref>=0, then S
a1=1, S
b2=0; S
b1by modulating wave and carrier wave V
c2relatively obtain, if V
ref>V
c2, S
b1=0, otherwise S
b1=1; S
a2by modulating wave and carrier wave V
c1relatively obtain, if V
ref>V
c1, S
a2=1, otherwise S
a2=0;
(2) as modulating wave V
refbe in negative half-cycle, i.e. V
ref<0, then S
a1=0, S
b2=1; In order to make carrier wave and modulating wave compare, modulating wave being added 1 and obtaining revised modulating wave V
ref *, i.e. V
ref *=V
ref+ 1; S
b1by modulating wave V
ref *with carrier wave V
c2relatively obtain, if V
ref *>V
c2, S
b1=0, otherwise S
b1=1; S
a2by modulating wave V
ref *with carrier wave V
c1relatively obtain, if V
ref *>V
c1, S
a2=1, otherwise S
a2=0;
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2for the switch function of brachium pontis be connected with total output in module 2, V
c1, V
c2be two stacked triangular carriers, and V
c1>=V
c2>=0.
4. the modulator approach of a kind of suppression two H bridge cascaded inverter leakage currents according to right 1, it is characterized in that, the pwm signal producing method of the Switch State Combination in Power Systems of the second described in step 4 is,
(1) as modulating wave V
refbe in positive half period, i.e. V
ref>=0, then S
a1=1, S
b2=0; S
b1by modulating wave and carrier wave V
c1relatively obtain, if V
ref>V
c1, S
b1=0, otherwise S
b1=1; S
a2by modulating wave and carrier wave V
c2relatively obtain, if V
ref>V
c2, S
a2=1, otherwise S
a2=0;
(2) as modulating wave V
refbe in negative half-cycle, i.e. V
ref<0, then S
a1=0, S
b2=1; In order to make carrier wave and modulating wave compare, modulating wave being added 1 and obtaining revised modulating wave V
ref *, i.e. V
ref *=V
ref+ 1; S
b1by modulating wave V
ref *with carrier wave V
c1relatively obtain, if V
ref *>V
c1, S
b1=0, otherwise S
b1=1; S
a2by modulating wave V
ref *with carrier wave V
c2relatively obtain, if V
ref *>V
c2, S
a2=1, otherwise S
a2=0;
Wherein, S
a1for the switch function of brachium pontis be connected with total output in module 1, S
b1for the switch function of brachium pontis be connected with module 2 in module 1, S
a2for the switch function of brachium pontis be connected with module 1 in module 2, S
b2for the switch function of brachium pontis be connected with total output in module 2, V
c1, V
c2be two stacked triangular carriers, and V
c1>=V
c2>=0.
5. the modulator approach of a kind of suppression two H bridge cascaded inverter leakage currents according to right 1, it is characterized in that, stacked triangular carrier described in step 4 is two synchronous stacked triangular carriers.
6. the modulator approach of a kind of suppression two H bridge cascaded inverter leakage currents according to right 1, it is characterized in that, stacked triangular carrier described in step 4 is the stacked triangular carrier of two antiphases.
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