CN104410310A - Neutral point clamped H-bridge photovoltaic inverter and method for inhibiting common mode leakage current - Google Patents

Neutral point clamped H-bridge photovoltaic inverter and method for inhibiting common mode leakage current Download PDF

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Publication number
CN104410310A
CN104410310A CN201410766186.1A CN201410766186A CN104410310A CN 104410310 A CN104410310 A CN 104410310A CN 201410766186 A CN201410766186 A CN 201410766186A CN 104410310 A CN104410310 A CN 104410310A
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switch
inverter
voltage
common mode
common
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CN201410766186.1A
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Chinese (zh)
Inventor
高峰
周立为
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Shandong University
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Shandong 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
    • 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
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/487—Neutral point clamped inverters
    • 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
    • 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 a neutral point clamped H-bridge photovoltaic inverter and method for inhibiting a common mode leakage current. The photovoltaic inverter comprises a photovoltaic cell panel, a DC side filter circuit, a single-phase full-bridge inverter circuit and an AC side filter circuit which are connected in series with one another in sequence, wherein a common mode leakage current inhibiting circuit is connected in series between the DC side filter circuit and the single-phase full-bridge inverter circuit; during the whole period of the grid voltage, by controlling the action of switches in the single-phase full-bridge inverter circuit and the common mode leakage current inhibiting circuit, the common mode voltage of the photovoltaic inverter is always kept Udc/2 under the high-frequency action of the switches, so that the intensity of the common mode leakage current is inhibited, and the switch modulation strategy of the photovoltaic inverter can avoid current waveform distortion caused by the fluctuation influence of the grid power or operation at non-unit power factors.

Description

For suppressing neutral point clamp type H bridge photovoltaic DC-to-AC converter and the method for common mode leakage current
Technical field
The present invention relates to a kind of non-isolated photovoltaic grid-connected inverter, particularly relating to a kind of for suppressing neutral point clamp type H bridge photovoltaic DC-to-AC converter and the method for work thereof of common mode leakage current.
Background technology
In recent years, along with the continuous consumption of fossil fuel in world wide, energy-intensive problem is day by day serious, and therefore, the research of regenerative resource is subject to countries in the world and more and more pays close attention to.Solar photovoltaic technology is a key areas of regenerative resource application, and photovoltaic DC-to-AC converter is the key component of grid-connected photovoltaic power generation system, and its Main Function is that the direct current sent by photovoltaic battery panel converts the alternating current with synchronized to.Photovoltaic combining inverter traditional in solar photovoltaic grid-connection system generally understands erector's frequency power transformer at output, to realize the adjustment to voltage and the isolation to electrical network, but Industrial Frequency Transformer volume is large, cost is high, loss is large, be unfavorable for the improvement of inverter whole efficiency, the research therefore for the non-isolated photovoltaic grid-connected inverter of no industrial frequency transformer becomes focus.In non-isolation type photovoltaic grid-connected inverting system; owing to there is no electrical isolation between inverter and electrical network, under the effect of inverter HF switch, common mode current can be produced; common mode current flows through the common mode loop of system, can produce common mode leakage current in the parasitic capacitance over the ground of photovoltaic panel.
The model of common-mode voltage and common mode current in traditional single phase H full-bridge inverter.Be illustrated in figure 1 the structure chart of conventional non-isolated type single-phase photovoltaic grid-connected system.In FIG, four switch motions of H4 circuit, under high frequency state, can excite a common-mode voltage U in power frequency period cm, because photovoltaic battery panel exists a stray capacitance C over the ground pv, therefore common-mode voltage can produce the common mode leakage current I flowing through stray capacitance, the earth and circuit part in circuit cm.The resonant tank of common mode current represents with dotted line and arrow in FIG.Common-mode voltage formula is:
U cm-AB＝(U AO+U BO)/2
The formula of common mode current can be expressed as:
I cm＝C pdU cm/dt
The common mode leakage current that non-isolation type photovoltaic inverting system produces can work the mischief to personal safety time serious, especially in traditional single-phase full-bridge inverter, if adopt unipolarity switch modulation strategy, common-mode voltage then can be made to produce larger fluctuation, and then bring serious common mode leakage problem.
Summary of the invention
The object of the invention is to overcome the above problems, proposing a kind of for suppressing neutral point clamp type H bridge photovoltaic DC-to-AC converter and the method for common mode leakage current.This single-phase inverter ensures that the common-mode voltage of system keeps constant in the process of switch motion, thus the size of common mode leakage current is inhibited, simultaneously under freewheeling state circuit topological structure can by photovoltaic module and electrical network isolation, avoid Power Exchange, thus improve efficiency, the switch modulation mode that this novel topological structure adopts in addition can also ensure inverter when unity power factor runs not by the impact of current zero-crossing point distortion.
To achieve these goals, the present invention adopts following technical scheme.
For suppressing a neutral point clamp type H bridge photovoltaic DC-to-AC converter for common mode leakage current, comprising:
The photovoltaic battery panel be sequentially connected in series, DC side filter circuit, single-phase full bridge inverter circuit and AC filter circuit; Common mode drain current suppressing circuit is connected in series with between single-phase full bridge inverter circuit at described DC side filter circuit;
Within the whole cycle of line voltage, by controlling the action of single-phase full bridge inverter circuit and common mode drain current suppressing circuit breaker in middle, the common-mode voltage of photovoltaic DC-to-AC converter is made to remain U under switch high-frequency action dc/ 2 is constant, wherein U dcfor DC voltage.
Described common mode drain current suppressing circuit comprises:
Be sequentially connected in series the switch S 5 between single-phase full bridge inverter circuit switch S 1 and switch S 2 and switch S 6;
Diode D1 and diode D2 series aiding connection connect to form series arm one, and the positive input of described series arm one is connected between switch S 2 and switch S 6, the forward output of series arm one is connected between switch S 1 and switch S 5;
Diode D3 and diode D4 series aiding connection connect to form series arm two, and the positive input of described series arm two is connected between switch S 2 and switch S 6, the forward output of series arm one is connected between switch S 1 and switch S 5.
Described common mode drain current suppressing circuit also allows for:
Be sequentially connected in series the switch S 5 between single-phase full bridge inverter circuit switch S 1 and switch S 2 and switch S 6;
The switch S 8 be sequentially connected in series and one end of switch S 7 is connected with DC side filter circuit, the other end is connected between switch S 5 and switch S 6;
Diode D1 and diode D2 series aiding connection connect to form series arm three, and the positive input of described series arm three is connected between switch S 2 and switch S 6, the forward output of series arm three is connected between switch S 1 and switch S 5.
Described switch S 5, S6, S7 and S8 are respectively the one in switching tube MOSFET or IGBT.
Described DC side filter circuit is filter capacitor C1 and C2 be connected in series.
Described AC filter circuit is filter inductance.
For suppressing a method of work for the neutral point clamp type H bridge photovoltaic DC-to-AC converter of common mode leakage current, comprising:
At the positive half period of line voltage, when inverter is in power stage state, switch S 1, S4 and S5 conducting, other switch OFF, now common-mode voltage U cm=U dc/ 2;
At the positive half period of line voltage, when inverter is in no-voltage freewheeling state, switch S 5 keeps conducting state, and S6 conducting, now common-mode voltage remains U cm=U dc/ 2;
At the negative half-cycle of line voltage, when inverter is in power stage state, switch S 2, S3 and S6 conducting, other switch OFF, now common-mode voltage U cm=U dc/ 2;
At the negative half-cycle of line voltage, when inverter is in no-voltage freewheeling state, switch S 6 keeps conducting state, and S5 conducting, now powder inverter common-mode voltage remains U cm=U dc/ 2.
For suppressing a method of work for the neutral point clamp type H bridge photovoltaic DC-to-AC converter of common mode leakage current, also allow for:
At the positive half period of line voltage, when inverter is in power stage state, switch S 1, S4 and S5 conducting, other switch OFF, now common-mode voltage U cm=U dc/ 2;
At the positive half period of line voltage, when inverter is in no-voltage freewheeling state, switch S 5 keeps conducting state, and S6, S7 and S8 conducting, now common-mode voltage remains U cm=U dc/ 2;
At the negative half-cycle of line voltage, when inverter is in power stage state, switch S 2, S3 and S6 conducting, other switch OFF, now common-mode voltage U cm=U dc/ 2;
At the negative half-cycle of line voltage, when inverter is in no-voltage freewheeling state, switch S 6 keeps conducting state, and S5, S7 and S8 conducting, now powder inverter common-mode voltage remains U cm=U dc/ 2.
Beneficial effect of the present invention:
Topological structure of the present invention is under the high frequency mo of switch, the common-mode voltage of inverter is made to remain the half of direct voltage, the common-mode voltage of guarantee system keeps constant in the process of switch motion, thus the size of common mode leakage current is inhibited, simultaneously under freewheeling state circuit topological structure can by photovoltaic module and electrical network isolation, avoid Power Exchange, thus improve efficiency.
Topological structure of the present invention is compared with traditional H full-bridge inverter, effectively solve the problem of current non-isolation type single-phase photovoltaic grid-connected inverter common mode leakage current, the switch modulation mode adopted can also ensure inverter when unity power factor runs not by the impact of current zero-crossing point distortion, and components and parts performance can be made full use of, improving inverter coefficient of safety, realizing the improvement to exporting the quality of power supply.
Accompanying drawing explanation
Fig. 1 is traditional H4 bridge photovoltaic combining inverter common mode loop equivalent circuit diagram;
Fig. 2 is photovoltaic DC-to-AC converter electrical block diagram in the embodiment of the present invention one;
Fig. 3 is photovoltaic DC-to-AC converter electrical block diagram in the embodiment of the present invention two.
Embodiment
Below in conjunction with accompanying drawing and embodiment, the invention will be further described.
A kind of be applied to suppress common mode leakage current non-isolation type single-phase full bridge photovoltaic combining inverter structure as shown in Figures 2 and 3.Comprise: the photovoltaic battery panel be sequentially connected in series, DC side filter circuit, single-phase full bridge inverter circuit and AC filter circuit; Common mode drain current suppressing circuit is connected in series with between single-phase full bridge inverter circuit at described DC side filter circuit;
Within the whole cycle of line voltage, by controlling the action of single-phase full bridge inverter circuit and common mode drain current suppressing circuit breaker in middle, the common-mode voltage of photovoltaic DC-to-AC converter is made to remain U under switch high-frequency action dc/ 2 is constant, wherein U dcfor DC voltage.DC side filter circuit is filter capacitor C1 and C2 be connected in series.AC filter circuit is filter inductance.
Embodiment one:
Common mode drain current suppressing circuit in inverter structure shown in Fig. 2 is on the basis of traditional single phase full bridge inverter, add two switching tube S5, S6 and four diode D1 to D4, two the switching tube S5 increased, the effect of S6 is for electric current provides continuous current circuit in the process of switch high-frequency action, ensure that system common-mode voltage is constant in the course of action of HF switch, in four diodes increased wherein two for providing afterflow can road, two other diode is used for half common-mode voltage being clamped to direct voltage in afterflow process, thus suppress the size of common mode leakage current further.
The modulation system of switch is divided into four-stage in the one-period of line voltage, is respectively pattern one to pattern four:
In the pattern one of the positive half period of line voltage, inverter is in power stage state, switch S 1 and S4, S5 conducting, other switch OFF, common-mode voltage U now cm=U dc/ 2, in the pattern two of electrical network positive half period, inverter is in no-voltage freewheeling state, and switch S 5 keeps conducting state, and S6 conducting, now common-mode voltage remains U cm=U dc/ 2.
In the negative half-cycle of line voltage, in like manner, in pattern three, inverter is in power stage state, switch S 2 and S3, S6 conducting, other switch OFF, now common-mode voltage U cm=U dc/ 2, in the pattern four of electrical network negative half-cycle, inverter is in no-voltage freewheeling state, and switch S 6 keeps conducting state, and S5 conducting, now powder inverter common-mode voltage remains U cm=U dc/ 2.
Embodiment two:
Common mode drain current suppressing circuit in inverter structure shown in Fig. 3 is on the basis of traditional H4 bridge inverter circuit, add four switching tube S5 to S8 and two diode D1, D2, wherein in whole power frequency period, the S1 to S6 under four on off states of pattern one to pattern four of inverter shown in Fig. 3 is identical with S1 to the S6 switch modulation strategy in embodiment one, S7 and S8 in inverter shown in Fig. 3 two switches are the complementary conducting with S1, S4 in line voltage positive half period, the complementary conducting with S2, S3 in negative half-cycle.
Like this within the whole cycle of line voltage, the common-mode voltage of inverter remains U dc/ 2, therefore common mode leakage current I cm=C pVdU cm/ dt will be suppressed greatly, thus eliminate the harm that the person or equipment are subject to leakage current.
By reference to the accompanying drawings the specific embodiment of the present invention is described although above-mentioned; but not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various amendment or distortion that creative work can make still within protection scope of the present invention.

Claims (8)

1., for suppressing a neutral point clamp type H bridge photovoltaic DC-to-AC converter for common mode leakage current, it is characterized in that, comprise:
The photovoltaic battery panel be sequentially connected in series, DC side filter circuit, single-phase full bridge inverter circuit and AC filter circuit; Common mode drain current suppressing circuit is connected in series with between single-phase full bridge inverter circuit at described DC side filter circuit;
Within the whole cycle of line voltage, by controlling the action of single-phase full bridge inverter circuit and common mode drain current suppressing circuit breaker in middle, the common-mode voltage of photovoltaic DC-to-AC converter is made to remain U under switch high-frequency action dc/ 2 is constant, wherein U dcfor DC voltage.
2. a kind of for suppressing the neutral point clamp type H bridge photovoltaic DC-to-AC converter of common mode leakage current as claimed in claim 1, it is characterized in that, described common mode drain current suppressing circuit comprises:
Be sequentially connected in series the switch S 5 between single-phase full bridge inverter circuit switch S 1 and switch S 2 and switch S 6;
Diode D1 and diode D2 series aiding connection connect to form series arm one, and the positive input of described series arm one is connected between switch S 2 and switch S 6, the forward output of series arm one is connected between switch S 1 and switch S 5;
Diode D3 and diode D4 series aiding connection connect to form series arm two, and the positive input of described series arm two is connected between switch S 2 and switch S 6, the forward output of series arm one is connected between switch S 1 and switch S 5.
3. a kind of for suppressing the neutral point clamp type H bridge photovoltaic DC-to-AC converter of common mode leakage current as claimed in claim 1, it is characterized in that, described common mode drain current suppressing circuit also allows for:
Be sequentially connected in series the switch S 5 between single-phase full bridge inverter circuit switch S 1 and switch S 2 and switch S 6;
The switch S 8 be sequentially connected in series and one end of switch S 7 is connected with DC side filter circuit, the other end is connected between switch S 5 and switch S 6;
Diode D1 and diode D2 series aiding connection connect to form series arm three, and the positive input of described series arm three is connected between switch S 2 and switch S 6, the forward output of series arm three is connected between switch S 1 and switch S 5.
4. a kind ofly as claimed in claim 2 or claim 3 it is characterized in that for suppressing the neutral point clamp type H bridge photovoltaic DC-to-AC converter of common mode leakage current, described switch S 5, S6, S7 and S8 are respectively the one in switching tube MOSFET or IGBT.
5. a kind ofly as claimed in claim 1 it is characterized in that for suppressing the neutral point clamp type H bridge photovoltaic DC-to-AC converter of common mode leakage current, described DC side circuit is two equal electric capacity C1 and C2 be connected in series.
6. a kind of for suppressing the neutral point clamp type H bridge photovoltaic DC-to-AC converter of common mode leakage current as claimed in claim 1, it is characterized in that, described AC filter circuit is filter inductance.
7. as claimed in claim 2 for suppressing a method of work for the neutral point clamp type H bridge photovoltaic DC-to-AC converter of common mode leakage current, it is characterized in that, comprising:
At the positive half period of line voltage, when inverter is in power stage state, switch S 1, S4 and S5 conducting, other switch OFF, now common-mode voltage U cm=U dc/ 2;
At the positive half period of line voltage, when inverter is in no-voltage freewheeling state, switch S 1, S4 turn off, and S5 keeps conducting state, and S6 conducting, now common-mode voltage remains U cm=U dc/ 2;
At the negative half-cycle of line voltage, when inverter is in power stage state, switch S 2, S3 and S6 conducting, other switch OFF, now common-mode voltage U cm=U dc/ 2;
At the negative half-cycle of line voltage, when inverter is in no-voltage freewheeling state, switch S 2, S3 turn off, and S6 keeps conducting state, and S5 conducting, now powder inverter common-mode voltage remains U cm=U dc/ 2.
8. as claimed in claim 3 for suppressing a method of work for the neutral point clamp type H bridge photovoltaic DC-to-AC converter of common mode leakage current, it is characterized in that, comprising:
At the positive half period of line voltage, when inverter is in power stage state, switch S 1, S4 and S5 conducting, other switch OFF, now common-mode voltage U cm=U dc/ 2;
At the positive half period of line voltage, when inverter is in no-voltage freewheeling state, switch S 1, S4 turn off, and S5 keeps conducting state, and S6, S7 and S8 conducting, now common-mode voltage remains U cm=U dc/ 2;
At the negative half-cycle of line voltage, when inverter is in power stage state, switch S 2, S3 and S6 conducting, other switch OFF, now common-mode voltage U cm=U dc/ 2;
At the negative half-cycle of line voltage, when inverter is in no-voltage freewheeling state, switch S 2, S3 turn off, and S6 keeps conducting state, and S5, S7 and S8 conducting, now powder inverter common-mode voltage remains U cm=U dc/ 2.
CN201410766186.1A 2014-12-11 2014-12-11 Neutral point clamped H-bridge photovoltaic inverter and method for inhibiting common mode leakage current Pending CN104410310A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105450059A (en) * 2015-12-22 2016-03-30 合肥工业大学 Modulation method for suppressing leakage current of two-H-bridge cascaded inverter
CN105553321A (en) * 2016-01-20 2016-05-04 南昌航空大学 Switch tube clamping type transformerless photovoltaic inverter topology
CN106208782A (en) * 2016-07-20 2016-12-07 合肥工业大学 Cascaded H-bridges photovoltaic inverter leakage current suppressing method based on Model Predictive Control
CN106253733A (en) * 2016-08-26 2016-12-21 合肥工业大学 Two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking
CN108418457A (en) * 2018-01-29 2018-08-17 江苏大学 Eight switching tube Transformer-free photovoltaic grid-connected inversion circuits of one kind and control method
CN116345930A (en) * 2023-05-31 2023-06-27 山东艾诺智能仪器有限公司 Alternating current power supply with low common mode interference and modulation method thereof

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105450059A (en) * 2015-12-22 2016-03-30 合肥工业大学 Modulation method for suppressing leakage current of two-H-bridge cascaded inverter
CN105553321A (en) * 2016-01-20 2016-05-04 南昌航空大学 Switch tube clamping type transformerless photovoltaic inverter topology
CN106208782A (en) * 2016-07-20 2016-12-07 合肥工业大学 Cascaded H-bridges photovoltaic inverter leakage current suppressing method based on Model Predictive Control
CN106253733A (en) * 2016-08-26 2016-12-21 合肥工业大学 Two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking
CN108418457A (en) * 2018-01-29 2018-08-17 江苏大学 Eight switching tube Transformer-free photovoltaic grid-connected inversion circuits of one kind and control method
CN108418457B (en) * 2018-01-29 2020-02-21 江苏大学 Eight-switch-tube transformer-free photovoltaic grid-connected inverter circuit and control method
CN116345930A (en) * 2023-05-31 2023-06-27 山东艾诺智能仪器有限公司 Alternating current power supply with low common mode interference and modulation method thereof
CN116345930B (en) * 2023-05-31 2023-08-08 山东艾诺智能仪器有限公司 Alternating current power supply with low common mode interference and modulation method thereof

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