CN104167946A - Midpoint clamping type single-phase non-isolated photovoltaic inverter main circuit topology with follow current switch - Google Patents

Midpoint clamping type single-phase non-isolated photovoltaic inverter main circuit topology with follow current switch Download PDF

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Publication number
CN104167946A
CN104167946A CN201410402491.2A CN201410402491A CN104167946A CN 104167946 A CN104167946 A CN 104167946A CN 201410402491 A CN201410402491 A CN 201410402491A CN 104167946 A CN104167946 A CN 104167946A
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China
Prior art keywords
switching tube
inverter
rectifier diode
rectifier
anode
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CN201410402491.2A
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Inventor
马海啸
叶海云
聂勋
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Nanjing Post and Telecommunication University
Nanjing University of Posts and Telecommunications
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Nanjing Post and Telecommunication University
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Priority to CN201410402491.2A priority Critical patent/CN104167946A/en
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy
    • Y02E10/56Power conversion systems, e.g. maximum power point trackers

Abstract

The invention discloses a midpoint clamping type single-phase non-isolated photovoltaic inverter main circuit topology with a follow current switch. According to the topology, firstly, the follow current switch (composed of a single-phase non-control rectifier bridge and a switching tube S5) is additionally arranged on the alternating current side of an H bridge inverter, the flow current switch enables flow current of the inverter not to flow through an input power source, the process of feeding energy back to the power source is omitted, and non-isolated photovoltaic inverter conversion efficiency is improved; secondly, two clamping diodes (D5 and D6) are additionally arranged between the midpoint of an inverter direct current input capacitor and the flow current switch, so that the inverter common mode voltage needed in the flow current stage is effectively clamped to be one half of the direct current input voltage, the inverter common mode feature is improved, common mode leakage current of a photovoltaic inverter is eliminated, and personnel and equipment safety is ensured when the midpoint clamping type single-phase non-isolated photovoltaic inverter main circuit topology is in use.

Description

The single-phase non-isolation photovoltaic DC-to-AC converter main circuit topology of neutral point clamp type with continued flow switch
Technical field
What the present invention relates to is a kind of main circuit topology of the single-phase non-isolation photovoltaic DC-to-AC converter of neutral point clamp type with continued flow switch, and this topology is applicable to efficiency and the higher photovoltaic generation occasion of personal safety equipment requirement, belongs to power electronics DC-AC conversion category.
Background technology
Photovoltaic combining inverter requires that efficiency is high, cost is low, can bear the large harmful effect of fluctuating of photovoltaic cell output voltage, and it exchanges output and also will meet the higher quality of power supply.
Whether can be divided into isolated form and non-isolation type with isolating transformer according to inverter.Isolated form photovoltaic DC-to-AC converter has been realized the electrical isolation of electrical network and cell panel, has ensured the person and device security.But its volume is large, and price is high, system changeover efficiency is lower.Non-isolation photovoltaic DC-to-AC converter structure, containing transformer, does not have the many advantages such as efficiency is high, volume is little, lightweight, cost is low.
At present, the peak efficiency of non-isolation photovoltaic DC-to-AC converter system can reach more than 98%.But removing of transformer makes to have electrical connection between input and output, due to the existence of cell panel direct-to-ground capacitance, can produce common mode leakage current when inverter work, increases system electromagnetic interference, affects the quality of grid current, the harm person and device security.
In order to ensure the person and device security, leakage current must be suppressed in certain scope.According to German DIN VDE 0126-1-1 standard, in the time that Ground leakage current instantaneous value is greater than 300mA, photovoltaic parallel in system must disconnect with electrical network in 0.3s.Therefore,, under the prerequisite of determining without common mode leakage current, the efficiency, the reduction device cost that improve as much as possible photovoltaic DC-to-AC converter become one of study hotspot of current photovoltaic DC-to-AC converter.
Summary of the invention
In order to eliminate common mode leakage current, guarantee the person and device security, the present invention proposes a kind of main circuit topology of the single-phase non-isolation photovoltaic DC-to-AC converter of neutral point clamp type with continued flow switch, and this topology can be improved inverter common mode characteristic, improves the conversion efficiency of inverter.
Technical solution of the present invention is: the main circuit topology of the single-phase non-isolation photovoltaic DC-to-AC converter of neutral point clamp type with continued flow switch as shown in Figure 1, is characterized in that: on the basis of single-phase full-bridge inverter, added continued flow switch (by single-phase rectifier bridge and the switching tube do not controlled s 5composition) and clamp circuit (by two electric capacity c dc1, c dc2with two diodes d 5, d 6composition).
Physical circuit topology is as follows: solar cell ( u pV) positive pole respectively with the first input capacitance ( c dc1) positive pole and the first switching tube ( s 1), the 3rd switching tube ( s 3) drain electrode be connected; Solar cell ( u pV) negative pole respectively with the second input capacitance ( c dc2) negative pole and second switch pipe ( s 2), the 4th switching tube ( s 4) source electrode be connected; The first switching tube ( s 1) source electrode and second switch pipe ( s 2) drain electrode be connected; The 3rd switching tube ( s 3) source electrode and the 4th switching tube ( s 4) drain electrode be connected; Four rectifier diodes for inverter AC ( d 1, d 2, d 3, d 4) composition rectifier bridge, wherein the first rectifier diode ( d 1) and the second rectifier diode ( d 2) common cathode, the 3rd rectifier diode ( d 3) and the 4th rectifier diode ( d 4) the common anode utmost point, the first rectifier diode ( d 1) anode and the 3rd rectifier diode ( d 3) negative electrode be connected, the second rectifier diode ( d 2) anode and the 4th rectifier diode ( d 4) negative electrode be connected; The first switching tube ( s 1) source electrode and second switch pipe ( s 2) drain electrode tie point A respectively with the first rectifier diode ( d 1) anode, the 3rd rectifier diode ( d 3) negative electrode and the first filter inductance ( l f1 ) one end be connected; The first filter inductance ( l f1 ) the other end respectively with filter capacitor ( c f ) one end and resistance ( r) one end be connected; The 3rd switching tube ( s 3) source electrode and the 4th switching tube ( s 4) drain electrode tie point B respectively with the second rectifier diode ( d 2) anode, the 4th rectifier diode ( d 4) negative electrode and the second filter inductance ( l f2 ) one end be connected; The second filter inductance ( l f2 ) the other end respectively with filter capacitor ( c f ) the other end and resistance ( r) the other end be connected; The 5th switching tube ( s 5) drain electrode be connected with rectifier bridge common cathode, source electrode is extremely connected with rectifier bridge common anode; The first clamping diode ( d 5) anode and the first input capacitance ( c dc1) negative pole, the second input capacitance ( c dc2) positive pole be connected, negative electrode is connected with the common cathode of rectifier bridge; The second clamping diode ( d 6) negative electrode and the first input capacitance ( c dc1) negative pole, the second input capacitance ( c dc2) positive pole be connected, anode is extremely connected with the common anode of rectifier bridge.
The present invention has following technique effect:
The single-phase non-isolation photovoltaic DC-to-AC converter output voltage of neutral point clamp type with continued flow switch is three level, identical with the output voltage of unipolarity modulation, is conducive to reduce the volume and weight of output filter.Adding of continued flow switch, makes the afterflow stage freewheel current power supply of not flowing through, and has saved this link of energy feedback power, has improved the conversion efficiency of inverter.Adding of clamp circuit, make afterflow stage continuous current circuit by clamp to 1/2nd of DC input voitage, can eliminate common mode leakage current completely.
Brief description of the drawings
The single-phase non-isolation photovoltaic DC-to-AC converter main circuit topology of neutral point clamp type of Fig. 1 band continued flow switch;
The single-phase non-isolation photovoltaic DC-to-AC converter mode figure of neutral point clamp type of Fig. 2 band continued flow switch;
The single-phase non-isolation photovoltaic DC-to-AC converter of neutral point clamp type of Fig. 3 band continued flow switch drives signal timing diagram.
Embodiment
Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail:
As shown in Figure 3, provided the control sequential chart of the present invention in a kind of control program, in figure, waveform is respectively from top to bottom: the first switching tube gate source voltage waveform ; Second switch pipe gate source voltage waveform ; The 3rd switching tube gate source voltage waveform ; The 4th switching tube gate source voltage waveform ; The 5th switching tube gate source voltage waveform .This non-isolation photovoltaic DC-to-AC converter can be divided into 4 kinds of operation modes within an inversion cycle, as shown in Figure 2, difference correspondence [ , ], [ , ], [ , ] and [ , ] four time periods.The operation principle of inverter while below briefly introducing each operation mode:
Mode 1:
As shown in Fig. 2 (a), [ , ] stage, switching tube , gate source voltage be high level, , in conducting state; Switching tube , with gate source voltage be zero, , with in off state.Electric current flows out from positive source, flows through , , load, , , finally flow back to power cathode.Now v aQ= v pV, v bQ=0, therefore inverter leg mid-point voltage v aB= v pV, common-mode voltage v cm=( v aQ+ v bQ)/2=0.5 v pV.
Mode 2:
As shown in Fig. 2 (b), [ , ] stage, switching tube , , with gate source voltage be zero, , , with in off state; Switching tube gate source voltage be high level, in conducting state.Inductive current afterflow, electric current is flowed through successively l f1 , load, l f2 , d 2, s 5, d 3; In the afterflow stage, solar panel output and electrical network disconnect.When , current potential higher than two of input voltage/for the moment, diode bear forward voltage conducting, , current potential by clamp the half to input voltage.When , current potential lower than two of input voltage/for the moment, diode bear forward voltage conducting, , current potential by clamp the half to input voltage.The whole afterflow stage, v aQ=0.5 v pV, v bQ=0.5 v pVtherefore, inverter leg mid-point voltage v aB=0, common-mode voltage v cm=( v aQ+ v bQ)/2=0.5 v pV.
Mode 3:
As shown in Fig. 2 (c), [ , ] stage, switching tube , gate source voltage be high level, , in conducting state; Switching tube , with gate source voltage be zero, , with in off state.Electric current flows out from positive source, flows through , , load, , , finally flow back to power cathode.Now v aQ=0, v bQ= v pVtherefore, inverter leg mid-point voltage v aB=- v pV, common-mode voltage v cm=( v aQ+ v bQ)/2=0.5 v pV.
Mode 4:
As shown in Fig. 2 (d), [ , ] stage, switching tube , , with gate source voltage be zero, , , with in off state; Switching tube gate source voltage be high level, in conducting state.Inductive current afterflow, electric current is flowed through successively l f2 , load, l f1 , d 1, s 5, d 4.In the afterflow stage, solar panel output and electrical network disconnect.When , current potential higher than two of input voltage/for the moment, diode bear forward voltage conducting, , current potential by clamp the half to input voltage.When , current potential lower than two of input voltage/for the moment, diode bear forward voltage conducting, , current potential by clamp the half to input voltage.The whole afterflow stage, v aQ=0.5 v pV, v bQ=0.5 v pVtherefore, inverter leg mid-point voltage v aB=0, common-mode voltage v cm=( v aQ+ v bQ)/2=0.5 v pV.
From analyzing above, the single-phase non-isolation photovoltaic DC-to-AC converter of neutral point clamp type with continued flow switch is using in suitable control strategy situation, inverter output voltage is three level, identical with the output voltage of unipolarity modulation, is conducive to reduce the volume and weight of output filter.Due to inverter afterflow stage continuous current circuit by clamp to 1/2nd of input voltage, the common-mode voltage of inverter is constant.Common-mode voltage is constant to be guaranteed to eliminate common mode leakage current completely, has reduced the electromagnetic interference of system, has ensured the safety of the person and equipment.In addition switch, s 5form continuous current circuit with rectifier bridge, thereby made the afterflow stage freewheel current power supply of not flowing through, saved this link of energy feedback power, improved the conversion efficiency of inverter.
In sum, the invention solves non-isolation photovoltaic DC-to-AC converter and can not eliminate the technical problems such as common mode leakage current, conversion efficiency be low completely, there is certain engineering using value.

Claims (2)

1. the main circuit topology of the single-phase non-isolation photovoltaic DC-to-AC converter of neutral point clamp type with continued flow switch, is characterized in that: on the basis of single-phase full-bridge inverter, added continued flow switch (by single-phase rectifier bridge and the switching tube do not controlled s 5composition) and clamp circuit (by two electric capacity c dc1, c dc2with two diodes d 5, d 6composition).
2. physical circuit topology is as follows: solar cell ( u pV) positive pole respectively with the first input capacitance ( c dc1) positive pole and the first switching tube ( s 1), the 3rd switching tube ( s 3) drain electrode be connected; Solar cell ( u pV) negative pole respectively with the second input capacitance ( c dc2) negative pole and second switch pipe ( s 2), the 4th switching tube ( s 4) source electrode be connected; The first switching tube ( s 1) source electrode and second switch pipe ( s 2) drain electrode be connected; The 3rd switching tube ( s 3) source electrode and the 4th switching tube ( s 4) drain electrode be connected; Four rectifier diodes for inverter AC ( d 1, d 2, d 3, d 4) composition rectifier bridge, wherein the first rectifier diode ( d 1) and the second rectifier diode ( d 2) common cathode, the 3rd rectifier diode ( d 3) and the 4th rectifier diode ( d 4) the common anode utmost point, the first rectifier diode ( d 1) anode and the 3rd rectifier diode ( d 3) negative electrode be connected, the second rectifier diode ( d 2) anode and the 4th rectifier diode ( d 4) negative electrode be connected; The first switching tube ( s 1) source electrode and second switch pipe ( s 2) drain electrode tie point A respectively with the first rectifier diode ( d 1) anode, the 3rd rectifier diode ( d 3) negative electrode and the first filter inductance ( l f1 ) one end be connected; The first filter inductance ( l f1 ) the other end respectively with filter capacitor ( c f ) one end and resistance ( r) one end be connected; The 3rd switching tube ( s 3) source electrode and the 4th switching tube ( s 4) drain electrode tie point B respectively with the second rectifier diode ( d 2) anode, the 4th rectifier diode ( d 4) negative electrode and the second filter inductance ( l f2 ) one end be connected; The second filter inductance ( l f2 ) the other end respectively with filter capacitor ( c f ) the other end and resistance ( r) the other end be connected; The 5th switching tube ( s 5) drain electrode be connected with rectifier bridge common cathode, source electrode is extremely connected with rectifier bridge common anode; The first clamping diode ( d 5) anode and the first input capacitance ( c dc1) negative pole, the second input capacitance ( c dc2) positive pole be connected, negative electrode is connected with the common cathode of rectifier bridge; The second clamping diode ( d 6) negative electrode and the first input capacitance ( c dc1) negative pole, the second input capacitance ( c dc2) positive pole be connected, anode is extremely connected with the common anode of rectifier bridge.
CN201410402491.2A 2014-08-16 2014-08-16 Midpoint clamping type single-phase non-isolated photovoltaic inverter main circuit topology with follow current switch Pending CN104167946A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106849728A (en) * 2017-03-15 2017-06-13 南京邮电大学 The control method of the Clamp three-phase non-isolated photovoltaic DC-to-AC converter with continued flow switch
CN106877716A (en) * 2017-03-15 2017-06-20 南京邮电大学 A kind of Clamp three-phase non-isolated photovoltaic DC-to-AC converter with continued flow switch

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CN203368360U (en) * 2010-08-17 2013-12-25 C·佩尔 Transformer-free single-phase photovoltaic (PV) inverter with improved circuit structure
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CN103051233A (en) * 2012-12-12 2013-04-17 东南大学 Non-isolated single-phase photovoltaic grid-connected inverter and on-off control timing sequence thereof
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106849728A (en) * 2017-03-15 2017-06-13 南京邮电大学 The control method of the Clamp three-phase non-isolated photovoltaic DC-to-AC converter with continued flow switch
CN106877716A (en) * 2017-03-15 2017-06-20 南京邮电大学 A kind of Clamp three-phase non-isolated photovoltaic DC-to-AC converter with continued flow switch

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Application publication date: 20141126