CN105450059B - Inhibit the modulator approach of two H bridge cascaded inverter leakage currents - Google Patents

Inhibit the modulator approach of two H bridge cascaded inverter leakage currents Download PDF

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CN105450059B
CN105450059B CN201510975756.2A CN201510975756A CN105450059B CN 105450059 B CN105450059 B CN 105450059B CN 201510975756 A CN201510975756 A CN 201510975756A CN 105450059 B CN105450059 B CN 105450059B
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CN105450059A (en
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王付胜
于世能
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
    • 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
    • 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

Abstract

The invention discloses it is a kind of inhibit two H bridge cascaded inverter leakage currents modulator approach, the described method includes：Calculate total parasitic capacitor voltage v of two H bridge cascaded inverters each on off statesNtOValue；Select total parasitic capacitor voltage vNtOFor vdcAll on off states；According to the requirement for exporting most level, reducing switch stress and balance module output power, two Switch State Combination in Power Systems are formed；Modulating wave is generated the pwm signal for meeting above-mentioned Switch State Combination in Power Systems, and be assigned to corresponding pin with two with mutually or compared with reverse phase stacking triangular carrier.The program need not increase additional hardware cost, can eliminate the leakage current for flowing into power grid, while inhibit single module leakage current, and this method only needs two carrier waves to be compared, and reduces the operand of processor, and realization method is simple.

Description

Inhibit the modulator approach of two H bridge cascaded inverter leakage currents
Technical field
The present invention relates to a kind of modulator approaches of single-phase two H bridge cascaded inverters, can especially inhibit two H of non-isolation type Bridge cascades the modulator approach of grid-connected photovoltaic inverter leakage current；It is suitable for parallel network power generation fields.
Background technology
Safe to use to ensure, 4105 standards of VDE are to (the leakage of photovoltaic (Photovoltaic, PV) grid-connected system common mode current Electric current) there is stringent limitation.The electrical isolation of PV and power grid can be realized using net side power frequency isolation transformer, inhibit leakage current, but It is that Industrial Frequency Transformer volume is big, weight is heavy, of high cost, system effectiveness is low.The electricity of PV and power grid is realized according to high frequency transformer Air bound is from can reduce system bulk, weight and cost, but power conversion is divided into several levels, and substantially do not change system effectiveness It is kind.And the conversion efficiency of gird-connected inverter and the generating efficiency of photovoltaic generating system are closely related.Therefore, efficient, small, Light-weight and at low cost non-isolated grid-connected inverter has a clear superiority.But it saves transformer and causes photovoltaic battery panel and electricity There is electrical connection between net, leakage current may be significantly increased, and bring conduction and radiation interference, increase grid-connected current harmonic wave And it is lost or even jeopardizes equipment and personnel safety.Therefore the leakage current for inhibiting non-isolated grid-connected inverter becomes research One of hot spot.
Existing non-isolation type single-phase photovoltaic grid-connected inverter is successfully applied to commercial sources at present, such as the Sunny of SMA companies Mini Central series photovoltaic inverters.But these structures are all based on the modified topology of single H bridges, are only applicable to small-power Occasion.And next-generation photovoltaic DC-to-AC converter needs to reach higher power grade and efficiency, therefore multi-electrical level inverter becomes master Want research object.Cascaded H-bridges multi-electrical level inverter have the characteristics that modularization easily expand, at low cost and output voltage quality it is high, And its DC side can be independently-powered by photovoltaic battery panel, and becoming its independent MPPT maximum power point tracking (MPPT) control can Can, thus cascaded H-bridges structure becomes the photovoltaic DC-to-AC converter structure of most prospect.Meanwhile cascaded H-bridges photovoltaic combining inverter Leakage current also becomes a major issue.
The drain current suppressing of cascaded H-bridges photovoltaic combining inverter has some achievements at present, such as entitled " Analysis and suppression of leakage current in cascaded-multilevel-inverter based PV systems,”Y.Zhou and H.Li,《IEEE Trans.Power Electron.》, 2014,29 (10), 5265-5277 (" cascade connection multi-level photovoltaic inverter leakage current is analyzed and inhibited ",《IEEE journals-power electronics periodical》, 2014 volume 29 10th phase page 5265-5277) article；This article proposes two kinds of drain current suppressing schemes, is adopted respectively in DC side and exchange side With different passive filters, but the program has the following disadvantages：
1) passive filter is mainly made of inductance and capacitance, using volume, the weight that can increase inverter in circuit And cost, while reduce the energy conversion efficiency of inverter；
2) leakage current harmonic wave scope is wider, and by such environmental effects, makes filter parameter design process complex；
3) Cascade H bridge inverter actual operating frequency is relatively low, and the major harmonic frequency of leakage current is relatively low, causes to filter The drain current suppressing effect of device is unsatisfactory.
Entitled " Hybrid Multicarrier Modulation to Reduce Leakage Current in a Transformerless Cascaded Multilevel Inverter for Photovoltaic Systems ", Rajasekar Selvamuthukumaran, Abhishek Garg, and Rajesh Gupta,《IEEE Transactions on Power Electron》, 2015,30 (4), 1779-1783 (" the mixing tune of reduction non-isolation type photovoltaic inverter leakage current System strategy ",《IEEE journals-power electronics periodical》, the 4th 1779-1783 pages of the phase of volume 30 in 2015) article；This article proposes A kind of modulation strategy for the two H bridge cascaded inverters realized based on two carrier waves, the deficiency of this method are as follows：
1) modulator approach cannot inhibit to flow into the leakage current of power grid, can not improve grid-connected current quality；
2) two stacking carrier waves with phase are the method use, but 180 ° of phase shift is needed every half of power frequency period carrier wave, This undoubtedly adds hardware realization difficulty.
It can be seen that the prior art can not be in the case where not increasing extra cost and not influencing grid-connected current quality, preferably Solve the current leakage of bridge Cascade H bridge inverter.
The content of the invention
The technical problem to be solved in the present invention proposes a kind of be not required additionally to overcome problems of the prior art Hardware can eliminate the leakage current for flowing into power grid, and inhibit single module leakage current, and two H of inhibition that realization method is simple and practicable The modulator approach of bridge cascaded inverter leakage current.
In order to complete the purpose of the present invention, the present invention proposes a kind of modulation for inhibiting two H bridge cascaded inverter leakage currents Method is selected including switching sequence；The key step of this modulator approach is as follows：
Step 1, if two module DC voltages of two H bridge cascaded inverters are identical, and it is denoted as vdc, calculate the cascade of two H bridges All 16 kinds of on off state (S of invertera1\Sb1\Sa2\Sb2) output voltage UO, 1 parasitic capacitor voltage v of moduleN1O, module 2 posts Raw capacitance voltage vN2OAnd total parasitic capacitor voltage vNtOValue,
UO=vdc(Sa1-Sb1+Sa2-Sb2),
vN1O=-0.5vdc(Sa1+Sb1-Sa2+Sb2),
vN2O=-0.5vdc(Sa1-Sb1+Sa2+Sb2),
vNtO=vN1O+vN2O；
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For in module 1 with 2 phase of module The switch function of bridge arm even, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with it is total defeated The switch function and satisfaction for the bridge arm that outlet is connected：
Step 2, according to step 1 be calculated as a result, selecting total parasitic capacitor voltage vNtOFor-vdcAll switch shapes State, wherein vdcFor each module DC voltage；
Step 3, according to step 2 selection as a result, being exported according to most level, reduction switch stress and balance module is exported The requirement of power forms following two Switch State Combination in Power Systems：
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 two kinds of Switch State Combination in Power Systems obtained by step 3, respectively following methods is selected to obtain pwm signal：
The first Switch State Combination in Power Systems, implementation method are stacked triangular carrier and relatively obtain pwm signal for modulating wave and two；
Second of Switch State Combination in Power Systems, implementation method are stacked triangular carrier and relatively obtain pwm signal for modulating wave and two.
Preferably, the method for Switch State Combination in Power Systems described in step 3 is：
In modulating wave positive half cycle, selecting switch state 1100 exports 0 level, and the output of selecting switch state 1000 or 1110+ vdcLevel, selecting switch state 1010 export+2vdcLevel；
In modulating wave negative half period, selecting switch state 0011 exports 0 level, and the output of selecting switch state 0001 or 0111- vdcLevel, selecting switch state 0101 export -2vdcLevel；
On off state 0011 is switched over 1100 in 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 VrefIn positive half period, i.e. Vref>=0, then Sa1=1, Sb2=0；Sb1By modulating wave and carrier wave Vc2 Compare to obtain, if Vref>Vc2, Sb1=0, otherwise Sb1=1；Sa2By modulating wave and carrier wave Vc1Compare to obtain, if Vref>Vc1, Sa2= 1, otherwise Sa2=0；
(2) as modulating wave VrefIn negative half-cycle, i.e. Vref<0, then Sa1=0, Sb2=1；In order to make carrier wave and modulating wave It is compared, modulating wave plus 1 is obtained into revised modulating wave Vref *, i.e. Vref *=Vref+1；Sb1By modulating wave Vref *With carrier wave Vc2Compare to obtain, if Vref *>Vc2, Sb1=0, otherwise Sb1=1；Sa2By modulating wave Vref *With carrier wave Vc1Compare to obtain, if Vref *> Vc1, Sa2=1, otherwise Sa2=0；
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For in module 1 with 2 phase of module The switch function of bridge arm even, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with it is total defeated The switch function for the bridge arm that outlet is connected, Vc1、Vc2Triangular carriers, and V are stacked for twoc1≥Vc2≥0。
Preferably, the pwm signal producing method of second of Switch State Combination in Power Systems is described in step 4,
(1) as modulating wave VrefIn positive half period, i.e. Vref>=0, then Sa1=1, Sb2=0；Sb1By modulating wave and carrier wave Vc1 Compare to obtain, if Vref>Vc1, Sb1=0, otherwise Sb1=1；Sa2By modulating wave and carrier wave Vc2Compare to obtain, if Vref>Vc2, Sa2= 1, otherwise Sa2=0；
(2) as modulating wave VrefIn negative half-cycle, i.e. Vref<0, then Sa1=0, Sb2=1；In order to make carrier wave and modulating wave It is compared, modulating wave plus 1 is obtained into revised modulating wave Vref *, i.e. Vref *=Vref+1；Sb1By modulating wave Vref *With carrier wave Vc1Compare to obtain, if Vref *>Vc1, Sb1=0, otherwise Sb1=1；Sa2By modulating wave Vref *With carrier wave Vc2Compare to obtain, if Vref *> Vc2, Sa2=1, otherwise Sa2=0；
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For in module 1 with 2 phase of module The switch function of bridge arm even, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with it is total defeated The switch function for the bridge arm that outlet is connected, Vc1、Vc2Triangular carriers, and V are stacked for twoc1≥Vc2≥0。
Preferably, stacking triangular carrier of the triangular carrier for two same-phases is stacked described in step 4.
Preferably, stacking triangular carrier of the triangular carrier for two antiphases is stacked described in step 4.
Compared with the prior art, beneficial effects of the present invention are as follows：
1st, additional hardware is not required, the volume, weight and cost of inverter will not be increased, while inverter will not be reduced Energy conversion efficiency.
2nd, the leakage current for flowing into power grid can be eliminated, and then improves power network current quality；It can inhibit single module leakage simultaneously Electric current reduces system loss and electromagnetic interference.
3rd, two carrier waves are only needed, and phase-shifting carrier wave need not be carried out, can just obtain the pwm signal of all switching tubes, it is real Existing mode is simple.
Description of the drawings
Fig. 1 is the overview flow chart of the present invention.
Fig. 2 is single-phase two H bridges tandem photovoltaic gird-connected inverter schematic diagram.
Fig. 3 is the first switch combination with phase carrier wave realization principle figure.
Fig. 4 is the first switch combination phase inverted carrier realization principle figure.
Fig. 5 is second of switch combination with phase carrier wave realization principle figure.
Fig. 6 is second of switch combination phase inverted carrier realization principle figure.
Specific embodiment
In order to make the purpose , technical scheme and advantage of the present invention be clearer, with reference to the accompanying drawings and embodiments, it is right The present invention is described in more detail.
The modulator approach disclosed by the invention for inhibiting two H bridge cascaded inverter leakage currents is applied to single-phase non-isolated two H bridges Tandem photovoltaic grid-connected system, systematic schematic diagram are as shown in Figure 2.In Fig. 2, module 1 and module 2 are H bridge structures, exchange side string Connection output, through two filter inductance L1And L2It is connected to power grid Eg.Each module DC side is powered by photovoltaic battery panel, direct current It presses as vdc。Cpv1And Cpv2It is the photovoltaic panel parasitic capacitance of module 1 and module 2 respectively, both end voltage is respectively vN1OAnd vN2O。
The on off state of each bridge arm can represent as follows by switch function in two H bridge cascaded inverters,
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For in module 1 with 2 phase of module The switch function of bridge arm even, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with it is total defeated The switch function for the bridge arm that outlet is connected.
On off state in two H bridge cascaded inverters a total of 16, each on off state can be by one group of switch function (Sa1\ Sb1\Sa2\Sb2) represent, such as 0101,1010.
For single-phase two H bridges tandem photovoltaic gird-connected inverter shown in Fig. 2, inhibition disclosed by the invention two H bridges cascade inversion The basic step of the modulator approach of device leakage current is as follows：
Referring to Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 and Fig. 6,
Step 1, if two module DC voltages of two H bridge cascaded inverters are identical, and it is denoted as vdc, calculate the cascade of two H bridges All 16 kinds of on off state (S of invertera1\Sb1\Sa2\Sb2) output voltage UO, 1 parasitic capacitor voltage v of moduleN1O, module 2 posts Raw capacitance voltage vN2OAnd total parasitic capacitor voltage vNtOValue,
UO=vdc(Sa1-Sb1+Sa2-Sb2),
vN1O=-0.5vdc(Sa1+Sb1-Sa2+Sb2),
vN2O=-0.5vdc(Sa1-Sb1+Sa2+Sb2),
vNtO=vN1O+vN2O；
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For in module 1 with 2 phase of module The switch function of bridge arm even, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with it is total defeated The switch function and satisfaction for the bridge arm that outlet is connected：
Result of calculation is as shown in table 1
1 on off state of table and common-mode voltage
Step 2, according to step 1 be calculated as a result, selecting total parasitic capacitor voltage vNtOFor-vdcAll switch shapes State, wherein vdcFor each module DC voltage, selection result is as shown in italics in table 1；
Step 3, according to step 2 selection as a result, being exported according to most level, reduction switch stress and balance module is exported The requirement of power forms following two Switch State Combination in Power Systems：
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：
In modulating wave positive half cycle, selecting switch state 1100 exports 0 level, and the output of selecting switch state 1000 or 1110+ vdcLevel, selecting switch state 1010 export+2vdcLevel；
In modulating wave negative half period, selecting switch state 0011 exports 0 level, and the output of selecting switch state 0001 or 0111- vdcLevel, selecting switch state 0101 export -2vdcLevel；
On off state 0011 is switched over 1100 in modulating wave zero crossing；
Step 4, to two kinds of Switch State Combination in Power Systems obtained by step 3, respectively following methods is selected to obtain pwm signal：
The first Switch State Combination in Power Systems, its implementation are stacked triangular carrier and relatively obtain PWM letters for modulating wave and two Number, wherein being stacked stacking triangular carrier of the triangular carrier for two same-phases or antiphase, specific manner of comparison is as follows：
(1) as modulating wave VrefIn positive half period, i.e. Vref>=0, then Sa1=1, Sb2=0；Sb1By modulating wave and carrier wave Vc2 Compare to obtain, if Vref>Vc2, Sb1=0, otherwise Sb1=1；Sa2By modulating wave and carrier wave Vc1Compare to obtain, if Vref>Vc1, Sa2= 1, otherwise Sa2=0；
(2) as modulating wave VrefIn negative half-cycle, i.e. Vref<0, then Sa1=0, Sb2=1；In order to make carrier wave and modulating wave It is compared, modulating wave plus 1 is obtained into revised modulating wave Vref *, i.e. Vref *=Vref+1；Sb1By modulating wave Vref *With carrier wave Vc2Compare to obtain, if Vref *>Vc2, Sb1=0, otherwise Sb1=1；Sa2By modulating wave Vref *With carrier wave Vc1Compare to obtain, if Vref *> Vc1, Sa2=1, otherwise Sa2=0；
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For in module 1 with 2 phase of module The switch function of bridge arm even, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with it is total defeated The switch function for the bridge arm that outlet is connected, Vc1、Vc2Triangular carriers, and V are stacked for twoc1≥Vc2≥0。
Second of Switch State Combination in Power Systems, its implementation are stacked triangular carrier and relatively obtain PWM letters for modulating wave and two Number, wherein being stacked stacking triangular carrier of the triangular carrier for two same-phases or antiphase.Specific implementation is as follows：
(1) as modulating wave VrefIn positive half period, i.e. Vref>=0, then Sa1=1, Sb2=0；Sb1By modulating wave and carrier wave Vc1 Compare to obtain, if Vref>Vc1, Sb1=0, otherwise Sb1=1；Sa2By modulating wave and carrier wave Vc2Compare to obtain, if Vref>Vc2, Sa2= 1, otherwise Sa2=0；
(2) as modulating wave VrefIn negative half-cycle, i.e. Vref<0, then Sa1=0, Sb2=1；In order to make carrier wave and modulating wave It is compared, modulating wave plus 1 is obtained into revised modulating wave Vref *, i.e. Vref *=Vref+1；Sb1By modulating wave Vref *With carrier wave Vc1Compare to obtain, if Vref *>Vc1, Sb1=0, otherwise Sb1=1；Sa2By modulating wave Vref *With carrier wave Vc2Compare to obtain, if Vref *> Vc2, Sa2=1, otherwise Sa2=0；
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For in module 1 with 2 phase of module The switch function of bridge arm even, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with it is total defeated The switch function for the bridge arm that outlet is connected, Vc1、Vc2Triangular carriers, and V are stacked for twoc1≥Vc2≥0。
With reference to specific embodiment, the present invention is described in more detail.
Embodiment 1
Step 1, if two module DC voltages of two H bridge cascaded inverters are identical, and it is denoted as vdc, calculate the cascade of two H bridges All 16 kinds of on off state (S of invertera1\Sb1\Sa2\Sb2) output voltage UO, 1 parasitic capacitor voltage v of moduleN1O, module 2 posts Raw capacitance voltage vN2OAnd total parasitic capacitor voltage vNtOValue,
UO=vdc(Sa1-Sb1+Sa2-Sb2),
vN1O=-0.5vdc(Sa1+Sb1-Sa2+Sb2),
vN2O=-0.5vdc(Sa1-Sb1+Sa2+Sb2),
vNtO=vN1O+vN2O；
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For in module 1 with 2 phase of module The switch function of bridge arm even, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with it is total defeated The switch function and satisfaction for the bridge arm that outlet is connected：
Result of calculation is as shown in table 1；
Step 2, according to step 1 be calculated as a result, selecting total parasitic capacitor voltage vNtOFor-vdcAll switch shapes State, wherein vdcFor each module DC voltage, selection result is as shown in italics in table 1；
Step 3, according to step 2 selection as a result, being exported according to most level, reduction switch stress and balance module is exported The requirement of power forms following two Switch State Combination in Power Systems：
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：
In modulating wave positive half cycle, selecting switch state 1100 exports 0 level, and the output of selecting switch state 1000 or 1110+ vdcLevel, selecting switch state 1010 export+2vdcLevel；
In modulating wave negative half period, selecting switch state 0011 exports 0 level, and the output of selecting switch state 0001 or 0111- vdcLevel, selecting switch state 0101 export -2vdcLevel；
On off state 0011 is switched over 1100 in modulating wave zero crossing；
Step 4, the first Switch State Combination in Power Systems obtained to step 3, its implementation are modulating wave and two same phases The stacking triangular carrier of position relatively obtains pwm signal, and specific manner of comparison is as follows：
(1) as modulating wave VrefIn positive half period, i.e. Vref>=0, then Sa1=1, Sb2=0；Sb1By modulating wave and carrier wave Vc2 Compare to obtain, if Vref>Vc2, Sb1=0, otherwise Sb1=1；Sa2By modulating wave and carrier wave Vc1Compare to obtain, if Vref>Vc1, Sa2= 1, otherwise Sa2=0；
(2) as modulating wave VrefIn negative half-cycle, i.e. Vref<0, then Sa1=0, Sb2=1；In order to make carrier wave and modulating wave It is compared, modulating wave plus 1 is obtained into revised modulating wave Vref *, i.e. Vref *=Vref+1；Sb1By modulating wave Vref *With carrier wave Vc2Compare to obtain, if Vref *>Vc2, Sb1=0, otherwise Sb1=1；Sa2By modulating wave Vref *With carrier wave Vc1Compare to obtain, if Vref *> Vc1, Sa2=1, otherwise Sa2=0；
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For in module 1 with 2 phase of module The switch function of bridge arm even, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with it is total defeated The switch function for the bridge arm that outlet is connected, Vc1、Vc2Triangular carriers, and V are stacked for twoc1≥Vc2≥0。
The realization principle figure of the present embodiment is as shown in figure 3, T is modulation wave period in Fig. 3, it is seen that this manner of comparison generates All on off states and the first Switch State Combination in Power Systems it is all identical.
Embodiment 2
The present embodiment compared with the stacking triangular carrier of two antiphases, realizes first in embodiment 1 using modulating wave Kind switch combination.For realization principle figure as shown in figure 4, T is modulation wave period in Fig. 4, carrier wave manner of comparison is same as Example 1, It can be seen that all on off states and the first Switch State Combination in Power Systems that this manner of comparison generates are all identical.
Embodiment 3
The present embodiment is adopted as modulating wave compared with the stacking triangular carrier of two same-phases, realizes the in embodiment 1 Two kinds of switch combinations, manner of comparison are：
(1) as modulating wave VrefIn positive half period, i.e. Vref>=0, then Sa1=1, Sb2=0；Sb1By modulating wave and carrier wave Vc1 Compare to obtain, if Vref>Vc1, Sb1=0, otherwise Sb1=1；Sa2By modulating wave and carrier wave Vc2Compare to obtain, if Vref>Vc2, Sa2= 1, otherwise Sa2=0；
(2) as modulating wave VrefIn negative half-cycle, i.e. Vref<0, then Sa1=0, Sb2=1；In order to make carrier wave and modulating wave It is compared, modulating wave plus 1 is obtained into revised modulating wave Vref *, i.e. Vref *=Vref+1；Sb1By modulating wave Vref *With carrier wave Vc1Compare to obtain, if Vref *>Vc1, Sb1=0, otherwise Sb1=1；Sa2By modulating wave Vref *With carrier wave Vc2Compare to obtain, if Vref *> Vc2, Sa2=1, otherwise Sa2=0；
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For in module 1 with 2 phase of module The switch function of bridge arm even, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with it is total defeated The switch function for the bridge arm that outlet is connected, Vc1、Vc2Triangular carriers, and V are stacked for twoc1≥Vc2≥0。
The same phase carrier wave realization principle figure of second of switch combination is as shown in figure 5, T is modulation wave period in Fig. 5, it is seen that this All on off states and second of Switch State Combination in Power Systems that kind manner of comparison generates are all identical.
Embodiment 4
The present embodiment compared with the stacking triangular carrier of two antiphases, realizes second in embodiment 1 using modulating wave Kind switch combination.For realization principle figure as shown in fig. 6, T is modulation wave period in Fig. 6, carrier wave manner of comparison is same as Example 3, It can be seen that all on off states and second of Switch State Combination in Power Systems that this manner of comparison generates are all identical.
Finally, corresponding drive signal is generated according to obtained switch function, according to the distribution principle of inverter distribute to Corresponding switching tube.
As it will be easily appreciated by one skilled in the art that the foregoing is merely illustrative of the preferred embodiments of the present invention, not to The limitation present invention, all any modification, equivalent and improvement made within the spirit and principles of the invention etc., should all include Within protection scope of the present invention.

Claims (6)

1. a kind of modulator approach for inhibiting two H bridge cascaded inverter leakage currents, selects including switching sequence, which is characterized in that this The key step of modulator approach is as follows：
Step 1, if two module DC voltages of two H bridge cascaded inverters are identical, and it is denoted as vdc, calculate the cascade inversion of two H bridges All 16 kinds of on off state (S of devicea1\Sb1\Sa2\Sb2) output voltage UO, 1 parasitic capacitor voltage v of moduleN1O, the parasitic electricity of module 2 Hold voltage vN2OAnd total parasitic capacitor voltage vNtOValue,
UO=vdc*(Sa1-Sb1+Sa2-Sb2),
vN1O=-0.5vdc*(Sa1+Sb1-Sa2+Sb2),
vN2O=-0.5vdc*(Sa1-Sb1+Sa2+Sb2),
vNtO=vN1O+vN2O；
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For the bridge being connected in module 1 with module 2 The switch function of arm, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with total output terminal phase The switch function of bridge arm even, and meet：
Step 2, according to step 1 be calculated as a result, selecting total parasitic capacitor voltage vNtOFor-vdcAll on off states, Middle vdcFor each module DC voltage；
Step 3, according to step 2 selection as a result, according to the most level of output, reducing switch stress and balance module output power Requirement, form following two Switch State Combination in Power Systems：
The first Switch State Combination in Power Systems：1010-1000-1100-0011-0001-0101；
Second of Switch State Combination in Power Systems：1010-1110-1100-0011-0111-0101；
Wherein, the corresponding switch function order of each on off state is：Sa1\Sb1\Sa2\Sb2；
Step 4, to two kinds of Switch State Combination in Power Systems obtained by step 3, respectively following methods is selected to obtain pwm signal：
The first Switch State Combination in Power Systems, implementation method are stacked triangular carrier and relatively obtain pwm signal for modulating wave and two；
Second of Switch State Combination in Power Systems, implementation method are stacked triangular carrier and relatively obtain pwm signal for modulating wave and two.
2. a kind of modulator approach for inhibiting two H bridge cascaded inverter leakage currents according to claim 1, which is characterized in that The method of Switch State Combination in Power Systems described in step 3 is：
In modulating wave positive half cycle, selecting switch state 1100 exports 0 level, 1000 or 1110 output+v of selecting switch statedcElectricity Flat, selecting switch state 1010 exports+2vdcLevel；
In modulating wave negative half period, selecting switch state 0011 exports 0 level, 0001 or 0111 output-v of selecting switch statedcElectricity Flat, selecting switch state 0101 exports -2vdcLevel；
On off state 0011 is switched over 1100 in modulating wave zero crossing.
3. a kind of modulator approach for inhibiting two H bridge cascaded inverter leakage currents according to claim 1, which 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 VrefIn positive half period, i.e. Vref>=0, then Sa1=1, Sb2=0；Sb1By modulating wave and carrier wave Vc2Compare It obtains, if Vref>Vc2, Sb1=0, otherwise Sb1=1；Sa2By modulating wave and carrier wave Vc1Compare to obtain, if Vref>Vc1, Sa2=1, it is no Then Sa2=0；
(2) as modulating wave VrefIn negative half-cycle, i.e. Vref<0, then Sa1=0, Sb2=1；In order to which carrier wave is made to be compared with modulating wave Compared with modulating wave plus 1 are obtained revised modulating wave Vref *, i.e. Vref *=Vref+1；Sb1By modulating wave Vref *With carrier wave Vc2Compare It obtains, if Vref *>Vc2, Sb1=0, otherwise Sb1=1；Sa2By modulating wave Vref *With carrier wave Vc1Compare to obtain, if Vref *>Vc1, Sa2= 1, otherwise Sa2=0；
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For the bridge being connected in module 1 with module 2 The switch function of arm, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with total output terminal phase The switch function of bridge arm even, Vc1、Vc2Triangular carriers, and V are stacked for twoc1≥Vc2≥0。
4. a kind of modulator approach for inhibiting two H bridge cascaded inverter leakage currents according to claim 1, which is characterized in that The pwm signal producing method of second of Switch State Combination in Power Systems is described in step 4,
(1) as modulating wave VrefIn positive half period, i.e. Vref>=0, then Sa1=1, Sb2=0；Sb1By modulating wave and carrier wave Vc1Compare It obtains, if Vref>Vc1, Sb1=0, otherwise Sb1=1；Sa2By modulating wave and carrier wave Vc2Compare to obtain, if Vref>Vc2, Sa2=1, it is no Then Sa2=0；
(2) as modulating wave VrefIn negative half-cycle, i.e. Vref<0, then Sa1=0, Sb2=1；In order to which carrier wave is made to be compared with modulating wave Compared with modulating wave plus 1 are obtained revised modulating wave Vref *, i.e. Vref *=Vref+1；Sb1By modulating wave Vref *With carrier wave Vc1Compare It obtains, if Vref *>Vc1, Sb1=0, otherwise Sb1=1；Sa2By modulating wave Vref *With carrier wave Vc2Compare to obtain, if Vref *>Vc2, Sa2= 1, otherwise Sa2=0；
Wherein, Sa1Switch function for the bridge arm being connected in module 1 with total output terminal, Sb1For what is be connected in module 1 with module 2 The switch function of bridge arm, Sa2Switch function for the bridge arm being connected in module 2 with module 1, Sb2For in module 2 with total output terminal The switch function of connected bridge arm, Vc1、Vc2Triangular carriers, and V are stacked for twoc1≥Vc2≥0。
5. a kind of modulator approach for inhibiting two H bridge cascaded inverter leakage currents according to claim 1, which is characterized in that Stacking triangular carrier of the triangular carrier for two same-phases is stacked described in step 4.
6. a kind of modulator approach for inhibiting two H bridge cascaded inverter leakage currents according to claim 1, which is characterized in that Stacking triangular carrier of the triangular carrier for two antiphases is stacked described in step 4.
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