CN106208654A - A kind of drain current suppressing method being applied to cascaded H-bridges photovoltaic DC-to-AC converter - Google Patents

A kind of drain current suppressing method being applied to cascaded H-bridges photovoltaic DC-to-AC converter Download PDF

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CN106208654A
CN106208654A CN201610701466.3A CN201610701466A CN106208654A CN 106208654 A CN106208654 A CN 106208654A CN 201610701466 A CN201610701466 A CN 201610701466A CN 106208654 A CN106208654 A CN 106208654A
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ref
bridge module
modulating wave
wave
bridge
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宣荣喜
滕飞
胡辉勇
唐子程
宋建军
舒斌
张鹤鸣
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Xidian University
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Xidian University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
    • H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
    • 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
    • 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 present invention provides a kind of drain current suppressing method being applied to cascaded H-bridges photovoltaic DC-to-AC converter, including: list, according to the on off state of four brachium pontis of two H bridge modules, 16 on off states that two H bridge modules comprise respectively；When the DC input voitage of two H bridge modules is identical, calculate the parasitic capacitor voltage of each H bridge module that each on off state is corresponding in described 16 on off states and the parasitic capacitor voltage sum that two H bridge modules are total；Select two identical all on off states of the total parasitic capacitor voltage sum of H bridge module and form Switch State Combination in Power Systems；According to Switch State Combination in Power Systems, compared with carrier wave by modulating wave, generate PWM drive signal and the switching tube of two H bridge modules is controlled, thus realize the suppression of leakage current.The present invention is steady state value by controlling cascaded H-bridges photovoltaic DC-to-AC converter parasitic capacitance, the leakage current in suppression cascaded H-bridges photovoltaic DC-to-AC converter.

Description

A kind of drain current suppressing method being applied to cascaded H-bridges photovoltaic DC-to-AC converter
Technical field
The present invention relates to photovoltaic power generation grid-connecting technical field, be specifically related to a kind of leakage based on cascaded H-bridges photovoltaic DC-to-AC converter Electric current suppressing method.
Background technology
Photovoltaic DC-to-AC converter (Photovoltaic inverter) is that a kind of electric power being made up of semiconductor device adjusts dress Put, be mainly used in direct current power to be converted into alternating electromotive force.Typically it is made up of boosting loop and inversion bridge type return.Boosting loop DC voltage needed for the output of the dc voltage boost of solar cell to inverter is controlled；Inversion bridge type return is then after boosting DC voltage be equivalently converted into the alternating voltage of conventional frequency.
For cascaded H-bridges photovoltaic DC-to-AC converter, the low-voltage direct side of each of which module can be carried out independently-powered by photovoltaic panel, just Controlling in the MPPT realizing each module, therefore H bridge topology is particularly well-suited to photovoltaic DC-to-AC converter.Compared with traditional inverter, Cascaded H-bridges photovoltaic DC-to-AC converter possesses clear superiority, and such as switching frequency is low, wave filter volume is little, be prone to modularity etc..
Cascaded H-bridges photovoltaic DC-to-AC converter reaches grid-connected required voltage by cascade module, and therefore such inverter need not become Depressor, reduces cost further, improves power density.But, cascaded H-bridges photovoltaic DC-to-AC converter lacks the buffer action of transformator, There is direct electrical equipment between photovoltaic panel and electrical network to connect, cause the parasitic capacitance between photovoltaic panel and the earth to form loop, produce Leakage current.So having a strong impact on efficiency and the reliability of system, even personal safety is threatened.Therefore, how killer stage The leakage current of connection H bridge photovoltaic DC-to-AC converter just becomes of crucial importance.
Summary of the invention
In order to solve above-mentioned leakage problem, the present invention provides a kind of electric leakage being applied to cascaded H-bridges photovoltaic DC-to-AC converter Stream suppressing method, described cascaded H-bridges photovoltaic DC-to-AC converter includes that two H bridge modules, described H bridge module include four switching tubes；Its In, described drain current suppressing method includes:
The on off state of four brachium pontis according to said two H bridge module lists 16 that said two H bridge module comprises On off state；
When the DC input voitage of said two H bridge module is identical, calculate each switch in described 16 on off states The parasitic capacitor voltage of each H bridge module that state is corresponding and the total parasitic capacitor voltage sum of said two H bridge module；
Select the identical all on off states of the total parasitic capacitor voltage sum of said two H bridge module and form on off state Combination；
According to described Switch State Combination in Power Systems, compared with carrier wave by modulating wave, generate PWM drive signal to described two The switching tube of individual H bridge module is controlled, thus realizes the suppression of leakage current.
In one embodiment of the invention, determine 16 on off states that said two H bridge module comprises, including:
Definition Sa1、Sb1、Sa2、Sb2It is respectively the switch function of pipe, said two H on the left brachium pontis of said two H bridge module one The switch function of pipe, said two H on the switch function of pipe, the left brachium pontis of said two H bridge module two on the right brachium pontis of bridge module one The switch function of pipe on the right brachium pontis of bridge module two, represents the shutoff of the described each switching tube of H bridge module by numeral 0,1 and leads respectively Logical state, according to Sa1/Sb1/Sa2/Sb2Different values, formed 0101,0100,0111,0110,0001,1101,0000, 1111,0011,1100,0010,1110,1001,1000,1011,1010 totally 16 on off states.
In one embodiment of the invention, the parasitic capacitor voltage sum selecting said two H bridge module total is identical All on off states form Switch State Combination in Power Systems, including:
The DC input voitage assuming each H bridge module is vpv, then whole magnitudes of voltage of said two H bridge module output For :+2vpv、+vpv、0、-vpv、-2vpv, the total parasitic capacitor voltage sum of said two H bridge module that selects to send as an envoy to is vpvInstitute Having on off state, when switching according to level, the minimum principle of switching tube action frequency forms described Switch State Combination in Power Systems.
In one embodiment of the invention, form described Switch State Combination in Power Systems, including:
When switching according to level, the principle that switching tube action frequency is minimum, form two kinds of Switch State Combination in Power Systems, wherein first Planting Switch State Combination in Power Systems is: 1010-1000-1100-0011-0001-0101, the most corresponding output level+2vpv、+vpv、0、 0、-vpv、-2vpv；The second Switch State Combination in Power Systems is: 1010-1110-1100-0011-0111-0101, respectively correspondence output electricity Flat+2vpv、+vpv、0、0、-vpv、-2vpv。
In one embodiment of the invention, described carrier wave uses four carrier signals tri1, tri2, tri3, tri4, its In, tri4>tri3>tri1>tri2,0<tri2<0.5,0.5<tri1<1,1<tri3<1.5,1.5<tri4<2；Described modulating wave vrefModulation degree is 0.9, and the first half cycle of described modulating wave is positioned at more than 1, and the later half cycle is positioned at less than 1.
In one embodiment of the invention, the output level corresponding to described on off state 1100 and 0011 is 0, institute State on off state 1100 and 0011 and only cross 1 switching carrying out switching tube at described modulating wave.
In one embodiment of the invention, described four carrier signals are homophase triangular carrier.
In one embodiment of the invention, modulating wave compares with carrier wave, generates PWM drive signal, including:
The PWM drive signal generating mode of the first Switch State Combination in Power Systems 1010-1000-1100-0011-0001-0101 Including:
As described modulating wave vrefWhen >=1, Sa1=1, Sb2=0；Sb1By described modulating wave vrefCompare with described carrier wave tri3 Obtain, if vref> tri3, Sb1=0, otherwise Sb1=1；Sa2By described modulating wave vrefCompare with described carrier wave tri4 and obtain, if vref> tri4, Sa2=1, otherwise Sa2=0；
As modulating wave vref< when 1, then Sa1=0, Sb2=1；Sb1By described modulating wave vrefCompare with described carrier wave tri2 Arrive, if vref> tri2, Sb1=0, otherwise Sb1=1；Sa2By described modulating wave vrefCompare with described carrier wave tri1 and obtain, if vref> Tri1, Sa2=1, otherwise Sa2=0；
The PWM drive signal generating mode of the second Switch State Combination in Power Systems 1010-1110-1100-0011-0111-0101 Including:
As described modulating wave vrefWhen >=1, Sa1=1, Sb2=0；Sb1By described modulating wave vrefCompare with described carrier wave tri4 Obtain, if vref> tri4, Sb1=0, otherwise Sb1=1；Sa2By described modulating wave vrefCompare with described carrier wave tri3 and obtain, if vref> tri3, Sa2=1, otherwise Sa2=0；
As described modulating wave vref< when 1, then Sa1=0, Sb2=1；Sb1By described modulating wave vrefWith described carrier wave tri1 ratio Relatively obtain, if vref> tri1, Sb1=0, otherwise Sb1=1；Sa2By described modulating wave vrefCompare with described carrier wave tri2 and obtain, if vref> tri2, Sa2=1, otherwise Sa2=0.
Compared with prior art, the invention have the benefit that and do not introducing new filter circuit and opening up not changing In the case of flutterring structure chart, the present invention, by new modulation strategy, makes parasitic capacitor voltage sum keep constant or power frequency is sinusoidal Amount, significantly decreases the leakage current of cascaded H-bridges photovoltaic DC-to-AC converter.
Accompanying drawing explanation
In order to understand the explanation embodiment of the present invention or technical scheme of the prior art, below will be to embodiment or existing skill In art description, the required accompanying drawing used is briefly described.Accompanying drawing in describing below is some embodiments of the present invention, right In those of ordinary skill in the art, on the premise of not paying creative work, it is also possible to obtain other according to these accompanying drawings Accompanying drawing.
The schematic diagram of the drain current suppressing method of a kind of cascaded H-bridges photovoltaic DC-to-AC converter that Fig. 1 provides for the embodiment of the present invention；
The signal of the drain current suppressing method of another cascaded H-bridges photovoltaic DC-to-AC converter that Fig. 2 provides for the embodiment of the present invention Flow chart；
The schematic diagram of a kind of two module-cascade H bridge photovoltaic DC-to-AC converters that Fig. 3 provides for the embodiment of the present invention；
Two module-cascade H bridge photovoltaic DC-to-AC converter equivalent models that Fig. 4 provides for the embodiment of the present invention；
The first Switch State Combination in Power Systems a kind of that Fig. 5 provides for the embodiment of the present invention realize schematic diagram；
A kind of the second Switch State Combination in Power Systems that Fig. 6 provides for the embodiment of the present invention realize schematic diagram.
Detailed description of the invention
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, the present invention is done Further detailed description, but embodiments of the present invention are not limited to this.
Embodiment one
Refer to the drain current suppressing side of a kind of cascaded H-bridges photovoltaic DC-to-AC converter that Fig. 1, Fig. 1 provide for the embodiment of the present invention The schematic diagram of method, the method comprises the steps: that described cascaded H-bridges photovoltaic DC-to-AC converter includes two H bridge modules, described H bridge mould Block includes four switching tubes；Wherein, described drain current suppressing method includes:
Step (a), lists said two H bridge module bag according to the on off state of four brachium pontis of said two H bridge module 16 on off states contained；
Step (b), when the DC input voitage of said two H bridge module is identical, calculates in described 16 on off states The parasitic capacitor voltage of each H bridge module that each on off state is corresponding and the total parasitic capacitor voltage of said two H bridge module Sum；
Step (c), selects the identical all on off states of the total parasitic capacitor voltage sum of said two H bridge module and is formed Switch State Combination in Power Systems；
Step (d), according to described Switch State Combination in Power Systems, is compared with carrier wave by modulating wave, generates PWM drive signal The switching tube of said two H bridge module is controlled, thus realizes the suppression of leakage current.
Wherein, for step a, may include that 16 on off states determining that said two H bridge module comprises, specifically For:
Definition Sa1、Sb1、Sa2、Sb2It is respectively the switch function of pipe, said two H on the left brachium pontis of said two H bridge module one The switch function of pipe, said two H on the switch function of pipe, the left brachium pontis of said two H bridge module two on the right brachium pontis of bridge module one The switch function of pipe on the right brachium pontis of bridge module two, represents the shutoff of the described each switching tube of H bridge module by numeral 0,1 and leads respectively Logical state, according to Sa1/Sb1/Sa2/Sb2Different values, formed 0101,0100,0111,0110,0001,1101,0000, 1111,0011,1100,0010,1110,1001,1000,1011,1010 totally 16 on off states.
Wherein, for step c, may include that the parasitic capacitor voltage sum selecting said two H bridge module total is identical All on off states form Switch State Combination in Power Systems, particularly as follows:
The DC input voitage assuming each H bridge module is vpv, then whole magnitudes of voltage of said two H bridge module output For :+2vpv、+vpv、0、-vpv、-2vpv, the total parasitic capacitor voltage sum of said two H bridge module that selects to send as an envoy to is vpvInstitute Having on off state, when switching according to level, the minimum principle of switching tube action frequency forms described Switch State Combination in Power Systems.
Wherein, during for switching according to level in step c, the minimum principle of switching tube action frequency forms described switch shape State combines, and may include that the described Switch State Combination in Power Systems of formation, particularly as follows:
When switching according to level, the principle that switching tube action frequency is minimum, form two kinds of Switch State Combination in Power Systems, wherein first Planting Switch State Combination in Power Systems is: 1010-1000-1100-0011-0001-0101, the most corresponding output level+2vpv、+vpv、0、 0、-vpv、-2vpv；The second Switch State Combination in Power Systems is: 1010-1110-1100-0011-0111-0101, respectively correspondence output electricity Flat+2vpv、+vpv、0、0、-vpv、-2vpv。
Wherein, for step d, may include that described carrier wave uses four carrier signals tri1, tri2, tri3, tri4, Wherein, tri4>tri3>tri1>tri2,0<tri2<0.5,0.5<tri1<1,1<tri3<1.5,1.5<tri4<2；Described modulation Ripple vrefModulation degree is 0.9, and the first half cycle of described modulating wave is positioned at more than 1, and the later half cycle is positioned at less than 1.
Wherein, for modulating wave in step d, may include that the output electricity corresponding to described on off state 1100 and 0011 Average out to 0, described on off state 1100 and 0011 only crosses 1 switching carrying out switching tube at described modulating wave.
Wherein, for carrier signal in step d, may include that described four carrier signals are homophase triangular carrier.
Wherein, for step d generates PWM drive signal, it is also possible to including:
The PWM drive signal generating mode of the first Switch State Combination in Power Systems 1010-1000-1100-0011-0001-0101 Including:
As described modulating wave vrefWhen >=1, Sa1=1, Sb2=0；Sb1By described modulating wave vrefCompare with described carrier wave tri3 Obtain, if vref> tri3, Sb1=0, otherwise Sb1=1；Sa2By described modulating wave vrefCompare with described carrier wave tri4 and obtain, if vref> tri4, Sa2=1, otherwise Sa2=0；
As modulating wave vref< when 1, then Sa1=0, Sb2=1；Sb1By described modulating wave vrefCompare with described carrier wave tri2 Arrive, if vref> tri2, Sb1=0, otherwise Sb1=1；Sa2By described modulating wave vrefCompare with described carrier wave tri1 and obtain, if vref> Tri1, Sa2=1, otherwise Sa2=0；
The PWM drive signal generating mode of the second Switch State Combination in Power Systems 1010-1110-1100-0011-0111-0101 Including:
As described modulating wave vrefWhen >=1, Sa1=1, Sb2=0；Sb1By described modulating wave vrefCompare with described carrier wave tri4 Obtain, if vref> tri4, Sb1=0, otherwise Sb1=1；Sa2By described modulating wave vrefCompare with described carrier wave tri3 and obtain, if vref> tri3, Sa2=1, otherwise Sa2=0；
As described modulating wave vref< when 1, then Sa1=0, Sb2=1；Sb1By described modulating wave vrefWith described carrier wave tri1 ratio Relatively obtain, if vref> tri1, Sb1=0, otherwise Sb1=1；Sa2By described modulating wave vrefCompare with described carrier wave tri2 and obtain, if vref> tri2, Sa2=1, otherwise Sa2=0.
The present embodiment, is controlled the switching tube of cascaded H-bridges photovoltaic DC-to-AC converter by PWM drive signal, solves level The problem that connection H bridge photovoltaic inverter leakage current is excessive, has reached not introduce new filter circuit, has not changed the premise of topological structure Under, by new modulation strategy, make parasitic capacitor voltage sum keep constant or power frequency sinusoidal quantity, reach to be substantially reduced Cascade H The effect of bridge photovoltaic inverter leakage current.
Embodiment two
Refer to the drain current suppressing of another cascaded H-bridges photovoltaic DC-to-AC converter that Fig. 2, Fig. 2 provide for the embodiment of the present invention The schematic flow diagram of method, technical scheme, on the basis of above-described embodiment, is described in detail by the present embodiment. Specifically, the method includes:
Step (a), sets up the schematic diagram of two module-cascade H bridge photovoltaic DC-to-AC converters, as it is shown on figure 3, wherein Cpv1And Cpv2 For the parasitic capacitance between photovoltaic array and the earth, vpv1And vpv2It is the DC input voitage of two modules, Cin1And Cin2For directly Stream side input capacitance, L1And L2For net side filter inductance, R1And R2For the dead resistance of net side filter inductance, vgFor line voltage, a1And b1It is respectively the left and right brachium pontis outfan of first H bridge module, a2And b2It is respectively the left and right brachium pontis of second H bridge module Outfan.
Step (b), row write out all 16 on off states that two H bridge modules comprise.Four of two of which H bridge module The upper switching tube of brachium pontis uses S respectivelya1, Sb1, Sa2, Sb2Switch function represents, particularly as follows:
Sa1Represent the switch function of pipe, S on the described left brachium pontis of H bridge module oneb1Represent on the described right brachium pontis of H bridge module one The switch function of pipe, Sa2Represent the switch function of pipe, S on the described left brachium pontis of H bridge module twob2Represent the described right bridge of H bridge module two The switch function of pipe on arm；Each switch function uses 1 representation switch pipe conducting, and 0 representation switch pipe turns off, and lower switching tube is with upper Switching tube complementary duty.
Step (c), calculates the parasitic capacitance of each H bridge module that each on off state is corresponding in whole 16 on off states Voltage and the total parasitic capacitor voltage sum of said two H bridge module.
Fig. 4 is the cascaded H-bridges photovoltaic DC-to-AC converter equivalent model of two modules.Wherein, va1n1、vb1n1、va2n2And vb2n2Respectively For each brachium pontis outfan a1、b1、a2And b2To common point n1And n2Voltage.As a example by the positive half period of power network current, it is assumed that net Side filter inductance L1=L2, owing to leakage current is the least, therefore L1And L2The voltage approximately equal of upper generation and be vL, meanwhile, the filter of net side The voltage of ripple inductance parasitic resistance is vR；
According to Fig. 4, Kirchhoff's law can obtain formula:
- v a 1 n 1 + v L + v R + v g + v c p v 1 = 0 - v b 2 n 2 - v L - v R + v c p v 2 = 0 - v b 1 n 1 + v a 2 n 2 - v c p v 2 + v c p v 1 = 0
Can be obtained by above three formulas:
v c p v 1 = v a 1 n 1 + v b 1 n 1 2 - v a 2 n 2 - v b 2 n 2 2 - v g 2
v c p v 2 = v a 1 n 1 - v b 1 n 1 2 + v a 2 n 2 + v b 2 n 2 2 - v g 2
Due to line voltage vgPredominantly power frequency component, the least to the influence of leakage current in parasitic capacitance, analysis hereafter Do not consider further that, therefore parasitic capacitance Cpv1And Cpv2Voltage vcpv1And vcpv2Can be expressed as:
v &prime; c p v 1 = v a 1 n 1 + v b 1 n 1 2 - v a 2 n 2 - v b 2 n 2 2
v &prime; c p v 2 = v a 1 n 1 - v b 1 n 1 2 + v a 2 n 2 + v b 2 n 2 2
Step (d), forms total output voltage, the on off state of two cascaded H-bridges modules, the parasitism of each H bridge module Capacitance voltage and the relation table of the total parasitic capacitor voltage sum of two H bridge modules, as shown in table 1.Wherein vabFor total output Voltage, Sa1、Sb1、Sa2、Sb2It is the switch function of four brachium pontis switching tubes of two H bridge modules, v 'cpv1Parasitic electricity for module one Hold voltage, v 'cpv2For the parasitic capacitor voltage of module two, v 'cpv1+v′cpv2It is the parasitic capacitor voltage sum of two H bridge modules, The level output of two H bridge modules is respectively as follows: 2vpv、vpv、0、-vpvWith-2vpv。
The on off state of 1 two H bridge modules of table and parasitic capacitor voltage
Step (e), according to the data result of table 1, host age preference capacitance voltage sum is vpvAll on off states, and root When switching according to level, the principle composition the following two kinds Switch State Combination in Power Systems that switching tube action frequency is minimum, it is respectively as follows: 1010- 1000-1100-0011-0001-0101 and 1010-1110-1100-0011-0111-0101.
Step (f), according to the either switch combinations of states of cascaded H-bridges module, generates PWM drive signal switch tube and carries out Controlling, its implementation is modulating wave and four synchronous carrier waves compare and obtain pwm signal.
Wherein, four carrier signals are tri1, tri2, tri3, tri4, meet: tri4>tri3>tri1>tri2,0< Tri2 < 0.5,0.5 < tri1 < 1,1 < tri3 < 1.5,1.5 < tri4 < 2.Modulating wave vrefModulation degree is 0.9, and the cycle is T, front half cycle Phase is positioned at more than 1, and the later half cycle is positioned at less than 1.
Realizing the first Switch State Combination in Power Systems of embodiment as shown in Figure 5, concrete manner of comparison is as follows:
(1) as modulating wave vrefWhen >=1, Sa1=1, Sb2=0；Sb1Compared with carrier wave tri3 by modulating wave and obtain, if vref> Tri3, Sb1=0, otherwise Sb1=1；Sa2Compared with carrier wave tri4 by modulating wave and obtain, if vref> tri4, Sa2=1, otherwise Sa2= 0；
(2) as modulating wave vref< when 1, then Sa1=0, Sb2=1；Sb1By modulating wave vrefCompare with carrier wave tri2 and obtain, if vref> tri2, Sb1=0, otherwise Sb1=1；Sa2By modulating wave vrefCompare with carrier wave tri1 and obtain, if vref> tri1, Sa2=1, no Then Sa2=0；
Realizing the second Switch State Combination in Power Systems of embodiment as shown in Figure 6, concrete manner of comparison is as follows:
(1) as modulating wave vrefWhen >=1, Sa1=1, Sb2=0；Sb1Compared with carrier wave tri4 by modulating wave and obtain, if vref> Tri4, Sb1=0, otherwise Sb1=1；Sa2Compared with carrier wave tri3 by modulating wave and obtain, if vref> tri3, Sa2=1, otherwise Sa2= 0；
(2) as modulating wave vref< when 1, then Sa1=0, Sb2=1；Sb1By modulating wave vrefCompare with carrier wave tri1 and obtain, if vref> tri1, Sb1=0, otherwise Sb1=1；Sa2By modulating wave vrefCompare with carrier wave tri2 and obtain, if vref> tri2, Sa2=1, no Then Sa2=0.
Above content is to combine concrete preferred implementation further description made for the present invention, it is impossible to assert Being embodied as of the present invention is confined to these explanations.For general technical staff of the technical field of the invention, On the premise of present inventive concept, it is also possible to make some simple deduction or replace, all should be considered as belonging to the present invention's Protection domain.

Claims (8)

1. being applied to a drain current suppressing method for cascaded H-bridges photovoltaic DC-to-AC converter, described cascaded H-bridges photovoltaic DC-to-AC converter includes two Individual H bridge module, described H bridge module includes four switching tubes, it is characterised in that described drain current suppressing method includes:
The on off state of four brachium pontis according to said two H bridge module is determined 16 that said two H bridge module comprises and is opened Off status；
When the DC input voitage of said two H bridge module is identical, calculate each on off state in described 16 on off states The parasitic capacitor voltage of corresponding each H bridge module and the total parasitic capacitor voltage sum of said two H bridge module；
Select the identical all on off states of the total parasitic capacitor voltage sum of said two H bridge module and form on off state group Close；
According to described Switch State Combination in Power Systems, compared with carrier wave by modulating wave, generate PWM drive signal to said two H The switching tube of bridge module is controlled, thus realizes the suppression of leakage current.
Method the most according to claim 1, it is characterised in that determine 16 switches that said two H bridge module comprises State, including:
Definition Sa1、Sb1、Sa2、Sb2It is respectively the switch function of pipe, said two H bridge mould on the left brachium pontis of said two H bridge module one The switch function of pipe, said two H bridge mould on the switch function of pipe, the left brachium pontis of said two H bridge module two on the right brachium pontis of block one The switch function of pipe on the right brachium pontis of block two, represents shutoff and the conducting shape of the described each switching tube of H bridge module respectively by numeral 0,1 State, according to Sa1/Sb1/Sa2/Sb2Different values, formed 0101,0100,0111,0110,0001,1101,0000,1111, 0011,1100,0010,1110,1001,1000,1011,1010 totally 16 on off states.
Method the most according to claim 1, it is characterised in that select the parasitic capacitor voltage that said two H bridge module is total All on off states that sum is identical form Switch State Combination in Power Systems, including:
The DC input voitage assuming each H bridge module is vpv, then whole magnitudes of voltage of said two H bridge module output are :+ 2vpv、+vpv、0、-vpv、-2vpv, the total parasitic capacitor voltage sum of said two H bridge module that selects to send as an envoy to is vpvAll open Off status, when switching according to level, the minimum principle of switching tube action frequency forms described Switch State Combination in Power Systems.
Method the most according to claim 3, it is characterised in that form described Switch State Combination in Power Systems, including:
When switching according to level, the principle that switching tube action frequency is minimum, form two kinds of Switch State Combination in Power Systems, wherein the first is opened Off status is combined as: 1010-1000-1100-0011-0001-0101, the most corresponding output level+2vpv、+vpv、0、0、- vpv、-2vpv；The second Switch State Combination in Power Systems is: 1010-1110-1100-0011-0111-0101, the most corresponding output level+ 2vpv、+vpv、0、0、-vpv、-2vpv。
Method the most according to claim 4, it is characterised in that described carrier wave use four carrier signals tri1, tri2, Tri3, tri4, wherein, tri4>tri3>tri1>tri2,0<tri2<0.5,0.5<tri1<1,1<tri3<1.5,1.5<tri4< 2；Described modulating wave vrefModulation degree is 0.9, and the first half cycle of described modulating wave is positioned at more than 1, and the later half cycle is positioned at less than 1.
Method the most according to claim 5, it is characterised in that the output electricity corresponding to described on off state 1100 and 0011 Average out to 0, described on off state 1100 and 0011 only crosses 1 switching carrying out switching tube at described modulating wave.
Method the most according to claim 6, it is characterised in that described four carrier signals are homophase triangular carrier.
Method the most according to claim 7, it is characterised in that modulating wave compares with carrier wave, generates PWM and drives letter Number, including:
The PWM drive signal generating mode of the first Switch State Combination in Power Systems 1010-1000-1100-0011-0001-0101 includes:
As described modulating wave vrefWhen >=1, Sa1=1, Sb2=0；Sb1By described modulating wave vrefCompare with described carrier wave tri3 Arrive, if vref> tri3, Sb1=0, otherwise Sb1=1；Sa2By described modulating wave vrefCompare with described carrier wave tri4 and obtain, if vref> Tri4, Sa2=1, otherwise Sa2=0；
As modulating wave vref< when 1, then Sa1=0, Sb2=1；Sb1By described modulating wave vrefCompare with described carrier wave tri2 and obtain, if vref> tri2, Sb1=0, otherwise Sb1=1；Sa2By described modulating wave vrefCompare with described carrier wave tri1 and obtain, if vref> tri1, Sa2=1, otherwise Sa2=0；
The PWM drive signal generating mode of the second Switch State Combination in Power Systems 1010-1110-1100-0011-0111-0101 includes:
As described modulating wave vrefWhen >=1, Sa1=1, Sb2=0；Sb1By described modulating wave vrefCompare with described carrier wave tri4 Arrive, if vref> tri4, Sb1=0, otherwise Sb1=1；Sa2By described modulating wave vrefCompare with described carrier wave tri3 and obtain, if vref> Tri3, Sa2=1, otherwise Sa2=0；
As described modulating wave vref< when 1, then Sa1=0, Sb2=1；Sb1By described modulating wave vrefCompare with described carrier wave tri1 Arrive, if vref> tri1, Sb1=0, otherwise Sb1=1；Sa2By described modulating wave vrefCompare with described carrier wave tri2 and obtain, if vref> Tri2, Sa2=1, otherwise Sa2=0.
CN201610701466.3A 2016-08-22 2016-08-22 A kind of drain current suppressing method being applied to cascaded H-bridges photovoltaic DC-to-AC converter Pending CN106208654A (en)

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