CN102157955A - Single-phase non-isolation type photovoltaic grid-connected inverter and control method - Google Patents

Single-phase non-isolation type photovoltaic grid-connected inverter and control method Download PDF

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Publication number
CN102157955A
CN102157955A CN2011100475384A CN201110047538A CN102157955A CN 102157955 A CN102157955 A CN 102157955A CN 2011100475384 A CN2011100475384 A CN 2011100475384A CN 201110047538 A CN201110047538 A CN 201110047538A CN 102157955 A CN102157955 A CN 102157955A
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China
Prior art keywords
brachium pontis
switching tube
frequency
power
operated
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CN2011100475384A
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Chinese (zh)
Inventor
刘伟增
刘小刚
张新涛
吴军利
梁欢迎
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特变电工新疆新能源股份有限公司
特变电工西安电气科技有限公司
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Priority to CN2011100475384A priority Critical patent/CN102157955A/en
Publication of CN102157955A publication Critical patent/CN102157955A/en

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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS 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
    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48Conversion 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
    • H02M7/53Conversion 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
    • H02M7/537Conversion 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
    • H02M7/5387Conversion 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
    • H02M7/5388Conversion 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 asymmetrical configuration of switches
    • H02M1/123
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS 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
    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48Conversion 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
    • H02M7/483Converters with outputs that each can have more than two voltages levels
    • H02M7/487Neutral point clamped inverters
    • 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 single-phase non-isolation type photovoltaic grid-connected inverter and a control method. The photovoltaic grid-connected inverter comprises a full-bridge circuit, a control circuit and a fly-wheel diode, wherein the control circuit is used for controlling conduction and cut-off of all switching tubes in the full-bridge circuit so as to convert direct current voltage generated by a photovoltaic array of the full-bridge circuit to sine wave voltage required for grid connection; and the fly-wheel diode is used for providing a fly-wheel loop so as to thoroughly disconnect the input side from a power grid. The photovoltaic grid-connected inverter can effectively inhibit common-mode current (namely drain current) of the single-phase non-isolation type photovoltaic grid-connected inverter and improve the electrical energy conversion efficiency of the inverter.

Description

A kind of single-phase non-isolation type photovoltaic combining inverter and control method
Technical field
The invention belongs to the active inverter technical field, relate to a kind of photovoltaic combining inverter, relate in particular to a kind of single-phase non-isolation type photovoltaic combining inverter and control method.
Background technology
Photovoltaic parallel in system is meant that the direct current that the solar energy photovoltaic array is produced is converted to the system that is connected with electrical network with the same amplitude of line voltage, the alternating current of frequency, homophase, and realization together through combining inverter.The normal isolated form photovoltaic combining inverter that adopts band power frequency or high frequency transformer has been guaranteed the electrical isolation between electrical network and the photovoltaic system like this in the photovoltaic parallel in system, thereby personnel protection is provided and has avoided common mode current between photovoltaic system and the ground.Yet if adopt Industrial Frequency Transformer, its volume is big, Heavy Weight and costing an arm and a leg; If adopt high frequency transformer, power conversion circuit will be divided into several grades, make that control is complicated, also reduce the efficient of system simultaneously.
In order to overcome the above-mentioned deficiency that the isolation type grid-connected system of transformer is arranged, transformerless non-isolation type inverter is studied.The single-phase photovoltaic grid-connected inverter of transformerless non-isolation type has the advantages that volume is little, efficient is high, price is low, wherein the most outstanding advantage is overall system efficiency can be brought up to 97~98%, these characteristics of transless topology have very big attraction for the higher photovoltaic parallel in system of cost of electricity-generating, so transformerless topology is widely used in the small-power photovoltaic parallel in system.Yet, in transformerless non-isolation type photovoltaic parallel in system, exist between electrical network and the photovoltaic array to be electrically connected.Owing to have parasitic capacitance between photovoltaic array and the ground, can produce common mode current (being leakage current), this has just increased electromagnetic radiation and potential safety hazard.Therefore, a problem that adopts the photovoltaic combining inverter of transless topological structure to properly settle is exactly how to eliminate the common mode current that is produced in the loop that parasitic capacitance forms.The origin cause of formation about common mode current specifically can be referring to " research that common mode current suppresses in the single-phase non-isolation type photovoltaic combining inverter " (Sun Longlin etc., the 11 academic annual meeting of power electronics association of China Institute of Electrical Engineering Technology) and " analysis of transless structure photovoltaic parallel in system common mode leakage current " (Ma Lin etc., solar energy journal 2009 the 30th volume the 7th phase 883-887 page or leaf).
In order to suppress common mode current, for example in application number is 200910234342.9 Chinese patent application " a kind of non-isolated grid-connected inverter and switch control time sequence thereof " a kind of photovoltaic combining inverter that can eliminate the common mode current of non-isolated grid-connected inverter is disclosed.This photovoltaic combining inverter carries out adding two controlled tr tubes on the basis of unipolarity modulation at full-bridge circuit and dividing potential drop electric capacity constitutes the two-way clamp branch road, drive signal to initiate switching tube is carried out control corresponding, make and carry out in the unipolarity modulation at circuit, cooperate switch control time sequence to realize that freewheeling circuit is when afterflow, the continuous current circuit current potential (promptly, exchange output point voltage over the ground) reduce to half of input direct voltage, thus reduce the common-mode voltage in the circuit.But also there is shortcoming in this photovoltaic combining inverter, this full-bridge circuit adopts the high frequency single-polarity mode to modulate, and as " research that common mode current suppresses in the single-phase non-isolation type photovoltaic combining inverter " (Sun Longlin etc., the 11 academic annual meeting of power electronics association of China Institute of Electrical Engineering Technology) pointed in, the common mode current that the common-mode voltage excitation common mode resonance loop that the full-bridge topology of employing unipolarity modulation is produced produces will reach several amperes and the linear increase along with the increase of switching frequency, that is to say, unipolarity modulation system itself just produces bigger common mode current (common mode current that adopts the common-mode voltage excitation of the full-bridge topology of bipolarity modulation to produce only be milliampere grade) inevitably, especially under the big situation of switching frequency.
Again for example, in application number is the patent application " Wechselrichter zum Umwandeln einer elektrischenGleichspannung in einen Wechselstrom oder eineWechselspannung " of EP 1369985 A2, disclose a kind of AC side brachium pontis mid point that proposes for the isolating transformer that removes in the full-bridge grid-connected inverter of Unipolar SPWM and added the new continuous current circuit of two-way gate-controlled switch set constructor at full-bridge circuit, but there is not to consider to reduce the continuous current circuit current potential in afterflow stage in this application, the continuous current circuit current potential is near input direct voltage Vin, compare between 0~0.5Vin with the common-mode voltage amplitude that the full-bridge topology of unipolarity modulation produces, its common-mode voltage and common mode current are all bigger, and the switching loss that produces is 2 times of the unipolarity modulation.
Summary of the invention
Technical problem to be solved by this invention is effectively to suppress the deficiency of common mode current at single-phase non-isolation type photovoltaic combining inverter in the prior art, provide a kind of single-phase non-isolation type photovoltaic combining inverter and control method, to suppress the generation of the common mode current in the non-isolation type combining inverter circuit better.
The technical scheme that solution the technology of the present invention problem is adopted is this single-phase non-isolation type photovoltaic combining inverter, comprises full-bridge circuit, control circuit and freewheeling circuit, wherein:
Full-bridge circuit, it is used for the direct voltage that photovoltaic array produces is converted to the sine voltage that satisfies the needs that are incorporated into the power networks, comprise first brachium pontis and second brachium pontis, first brachium pontis is provided with two or three or four switching tubes that have the reverse parallel connection diode that are connected in series, correspondingly be provided with four or three or two switching tubes that have the reverse parallel connection diode that are connected in series on second brachium pontis, first brachium pontis and second brachium pontis are in parallel with input DC power respectively, and the ac output end of first brachium pontis and second brachium pontis is connected to the network access filter inductance respectively;
Control circuit, it is used for respectively transmitting control signal to each switching tube of first brachium pontis and second brachium pontis, so that the switching tube conducting in the following manner in first brachium pontis and second brachium pontis or end: at positive half cycle of line voltage or negative half period, have three switching tube conductings on first brachium pontis and second brachium pontis, so that electric current flows to negative pole from the input DC power positive pole, described three switching tubes comprise one or two switching tube and the ac output end that is connected this brachium pontis of another brachium pontis and two or the switching tube between the input DC power negative pole between the ac output end that is connected anodal and this brachium pontis of input DC power of a brachium pontis in first brachium pontis and second brachium pontis, and be operated in high frequency successively according to order from the input DC power positive pole to negative pole, power frequency and high frequency, rest switch pipe in the win brachium pontis and second brachium pontis is ended, wherein, the described switching tube that is operated in high frequency is used for modulation output half-sinusoid voltage, and the described switching tube that is operated in power frequency is used to make the half-sinusoid voltage of the switching tube output that is operated in high frequency to form the positive half cycle or the negative half period of line voltage;
Two fly-wheel diodes, its be connected to the ac output end of a brachium pontis in first brachium pontis and second brachium pontis and another brachium pontis two switching tubes that work in high frequency and power frequency respectively be connected in series a little between, be used for when the switching tube that is operated in high frequency by the time form continuous current circuit with the switching tube that is operated in power frequency.
Preferably, described switching tube is mos field effect transistor or insulated gate bipolar transistor.
Preferably, control circuit adopts the DSP microprocessor.This control circuit is a high frequency SPWM modulator control signal to the control signal that the switching tube that works in high frequency sends; To be that positive half cycle or negative half period are permanent be high level to the control signal that sends to the switching tube that works in power frequency, and be low level square wave control signal in another half cycle perseverance.
Accordingly, the invention provides a kind of control method of single-phase non-isolation type photovoltaic combining inverter, this photovoltaic combining inverter comprises full-bridge circuit and two fly-wheel diodes, wherein, described full-bridge circuit is used for the direct voltage that photovoltaic array produces is converted to the sine voltage that satisfies the needs that are incorporated into the power networks, described two fly-wheel diodes are used for forming continuous current circuit with the switching tube that is operated in power frequency when the switching tube that is operated in high frequency ends, described method comprises: each switching tube in full-bridge circuit first brachium pontis and second brachium pontis transmits control signal respectively, so that the switching tube conducting in the following manner in first brachium pontis and second brachium pontis or end: at positive half cycle of line voltage or negative half period, have three switching tube conductings on first brachium pontis and second brachium pontis, so that electric current flows to negative pole from the input DC power positive pole, described three switching tubes comprise one or two switching tube and the ac output end that is connected this brachium pontis of another brachium pontis and two or the switching tube between the input DC power negative pole between the ac output end that is connected anodal and this brachium pontis of input DC power of a brachium pontis in first brachium pontis and second brachium pontis, and be operated in high frequency successively according to order from the input DC power positive pole to negative pole, power frequency and high frequency, rest switch pipe in the win brachium pontis and second brachium pontis is ended, wherein, the described switching tube that is operated in high frequency is used for modulation output half-sinusoid voltage, and the described switching tube that is operated in power frequency is used to make the half-sinusoid voltage of the switching tube output that is operated in high frequency to form the positive half cycle or the negative half period of line voltage.
As can be seen from the above technical solutions, the beneficial effect of the present invention's acquisition is:
(1) according to the topological structure and the control method of single-phase non-isolation type photovoltaic combining inverter of the present invention, the common-mode voltage output area of AC side output is identical with the common-mode voltage range of the interchange output of unipolarity modulation, therefore the current potential that is continuous current circuit has effectively reduced common-mode voltage and consequent common mode current in the single-phase non-isolation type photovoltaic combining inverter between 0~0.5Vin; Switching tube loss simultaneously is reduced, and has also therefore improved the transformation of electrical energy efficient of inverter;
(2) since the switching tube that is operated in high frequency and direct current input side anodal existence directly is connected with negative pole, when the switching tube that is operated in high frequency ended, continuous current circuit and direct current input side thoroughly disconnected, thereby reached the purpose that suppresses common mode current better.
Description of drawings
Fig. 1 is the topology diagram of photovoltaic combining inverter embodiment 1 of the present invention;
Fig. 2 is the fundamental diagram of embodiment 1 circuit when the positive half cycle of line voltage;
Fig. 3 is the fundamental diagram of embodiment 1 continuous current circuit when the positive half cycle of line voltage;
Fig. 4 is the fundamental diagram of embodiment 1 circuit when the line voltage negative half period;
Fig. 5 is the fundamental diagram of embodiment 1 at the continuous current circuit of line voltage negative half period;
Fig. 6 is the control signal sequential chart of the switching tube of embodiment 1;
Fig. 7 is the topology diagram of photovoltaic combining inverter embodiment 2 of the present invention;
Fig. 8 is the topology diagram of photovoltaic combining inverter embodiment 3 of the present invention.
Embodiment
For making those skilled in the art understand technical scheme of the present invention better, photovoltaic combining inverter of the present invention is described in further detail below in conjunction with the drawings and specific embodiments.
Photovoltaic combining inverter provided by the present invention designs based on full-bridge circuit, is intended to be converted to the sine voltage that satisfies the needs that are incorporated into the power networks by the conducting of the diode in the control full-bridge circuit and the direct voltage that ends the photovoltaic array generation.In addition, in order to suppress common mode current in the full-bridge circuit, between two brachium pontis of full-bridge circuit, connect two fly-wheel diodes respectively, in order to continuous current circuit to be provided, so that input side and electrical network thoroughly disconnect.
Specifically, photovoltaic combining inverter provided by the present invention comprises full-bridge circuit, control circuit and two fly-wheel diodes.
Wherein, full-bridge circuit comprises first brachium pontis and second brachium pontis, and six switching tubes that have the reverse parallel connection diode are set on first brachium pontis and second brachium pontis altogether, and the switching tube on each brachium pontis is connected in series.For example, two switching tubes that have the reverse parallel connection diode that are connected in series are set on first brachium pontis, four switching tubes that have the reverse parallel connection diode that are connected in series are set on second brachium pontis; Perhaps, with second brachium pontis three switching tubes that have the reverse parallel connection diode that are connected in series are set all on first brachium pontis; Perhaps, four switching tubes that have the reverse parallel connection diode that are connected in series are set on first brachium pontis, two switching tubes that have the reverse parallel connection diode that are connected in series are set on second brachium pontis.And, first brachium pontis and second brachium pontis are in parallel with input DC power respectively, that is to say, first brachium pontis and second brachium pontis are connected between the positive pole and negative pole of input DC power, at the inverter duration of work, electric current should flow to negative pole from the positive pole of input DC power.The ac output end of first brachium pontis and second brachium pontis is connected to the network access filter inductance respectively.Those skilled in the art are known, the ac output end of each brachium pontis generally is being connected in series a little of certain two switching tube on each brachium pontis in full-bridge circuit, the alternating current of this some output flows to the network access filter inductance and carries out filtering, therefore, here omit detailed description, and describe based on the notion of ac output end topological structure and operation principle in this manual photovoltaic combining inverter provided by the present invention to ac output end.
For the conducting of controlling the diode in the full-bridge circuit with by be converted to the sine voltage that satisfies the needs that are incorporated into the power networks with the direct voltage that photovoltaic array is produced, control circuit each switching tube in first brachium pontis and second brachium pontis respectively transmits control signal, so that the switching tube conducting in the following manner in first brachium pontis and second brachium pontis or end: at positive half cycle of line voltage or negative half period, have three switching tube conductings on first brachium pontis and second brachium pontis, so that electric current flows to negative pole from the input DC power positive pole.Described three switching tubes comprise one or two switching tube and the ac output end that is connected this brachium pontis of another brachium pontis and two or the switching tube between the input DC power negative pole between the ac output end that is connected anodal and this brachium pontis of input DC power of a brachium pontis in first brachium pontis and second brachium pontis, and be operated in high frequency successively according to order from the input DC power positive pole to negative pole, power frequency and high frequency, rest switch pipe in the win brachium pontis and second brachium pontis is ended, wherein, the described switching tube that is operated in high frequency is used for modulation output half-sinusoid voltage, and the described switching tube that is operated in power frequency is used to make the half-sinusoid voltage of the switching tube output that is operated in high frequency to form the positive half cycle or the negative half period of line voltage.
Two fly-wheel diodes be connected to the ac output end of a brachium pontis in first brachium pontis and second brachium pontis and another brachium pontis two switching tubes that work in high frequency and power frequency respectively be connected in series a little between, be used for when the switching tube that is operated in high frequency by the time form continuous current circuit with the switching tube that is operated in power frequency.
Fig. 1 is the topology diagram of photovoltaic combining inverter embodiment 1 of the present invention.Shown in the frame of broken lines among Fig. 1, the main topology of the photovoltaic combining inverter that present embodiment provided comprises full-bridge circuit and is connected two fly-wheel diodes between two brachium pontis of full-bridge circuit.
In Fig. 1, first brachium pontis of full-bridge circuit comprises four switching tubes that have the reverse parallel connection diode that are connected in series, promptly first brachium pontis is provided with switching tube VT1, VT2, VT3, the VT4 that is connected in series, diode D1, D2, D3, D4 respectively with switching tube VT1, VT2, VT3, VT4 reverse parallel connection.Concrete, the source electrode of switching tube VT1 links to each other with the drain electrode of switching tube VT2, and the source electrode of switching tube VT2 links to each other with the drain electrode of switching tube VT3, and the source electrode of switching tube VT3 links to each other with the drain electrode of switching tube VT4.The drain electrode of switching tube VT1 links to each other with the positive pole of DC side input power supply Vin, and the source electrode of switching tube VT4 links to each other with the negative pole of DC side input power supply Vin.The anode of diode D1, D2, D3, D4 is connected with the source electrode of switching tube VT1, VT2, VT3, VT4 respectively, and negative electrode is connected with the drain electrode of switching tube VT1, VT2, VT3, VT4 respectively.
Second brachium pontis of full-bridge circuit shown in Figure 1 comprises two switching tubes that have the reverse parallel connection diode that are connected in series, and promptly second brachium pontis is provided with switching tube VT5, the VT6 that is connected in series, diode D5, D6 respectively with switching tube VT5, VT6 reverse parallel connection.Concrete, the source electrode of switching tube VT5 links to each other with the drain electrode of switching tube VT6, and the anode of diode D5, D6 is connected with the source electrode of switching tube VT5, VT6 respectively, and negative electrode is connected with the drain electrode of switching tube VT5, VT6 respectively.The drain electrode of switching tube VT5 links to each other with the positive pole of DC side input power supply Vin, and the source electrode of switching tube VT6 links to each other with the negative pole of DC side input power supply Vin.
In the present invention, switching tube VT1, the VT2 on first brachium pontis and second brachium pontis, VT3, VT4, VT5, VT6 preferably select mos field effect transistor (MOSFET) or insulated gate bipolar transistor (IGBT) in the full-bridge circuit.General, the less and required switching speed of power is selected mos field effect transistor faster for use; If peak current and voltage are more greatly then select insulated gate bipolar transistor for use.Reverse parallel connection diode D1, D2, D3, D4, D5, when D6 disconnects at switching tube,, switching tube is played the effect of protection for the residual current that exists in the circuit provides continuous current circuit.
The ac output end of first brachium pontis and second brachium pontis lays respectively at being connected in series a little of centre of first brachium pontis and second brachium pontis.Concrete, being connected in series of the switching tube VT2 of first brachium pontis and VT3 a little is ac output end a, being connected in series of the switching tube VT5 of second brachium pontis and VT6 a little is ac output end b.Be connected with network access filter inductance L1 at ac output end a, ac output end b is connected with network access filter inductance L2, and network access filter inductance L1 is connected with electrical network Grid with L2, is used for the alternating current of full-bridge circuit output is carried out filtering, sends into electrical network then.
Control circuit sends control signal 1, control signal 2, control signal 3, control signal 4, control signal 5 and control signal 6 to the grid of switching tube VT1, VT2, VT3, VT4, VT5 and VT6 respectively.Specifically, at the positive half cycle of line voltage, control circuit transmits control signal to switching tube VT1, VT2 and VT6 respectively, so that switching tube VT1 is operated in high frequency, switching tube VT2 is operated in power frequency, switching tube VT6 is operated in high frequency, thereby makes electric current from the positive pole of DC side input power supply Vin, successively flow through VT1, VT2 and VT6, flow to the negative pole of DC side input power supply Vin then; Transmit control signal to switching tube VT3, VT4 and VT5 simultaneously, so that switching tube VT3, VT4 and VT5 end.At the line voltage negative half period, control circuit transmits control signal to switching tube VT5, VT3 and VT4 respectively, so that switching tube VT5 is operated in high frequency, switching tube VT3 is operated in power frequency, switching tube VT4 is operated in high frequency, thereby make electric current from the positive pole of DC side input power supply Vin, successively flow through switching tube VT5, VT3, VT4, flow to the negative pole of DC side input power supply Vin then; Transmit control signal to switching tube VT1, VT2 and VT6 simultaneously, so that switching tube VT1, VT2 and VT6 end.
In embodiment 1, control circuit adopts DSP F2812 microprocessor to handle.And control circuit is a high frequency SPWM modulator control signal to the control signal that the switching tube that works in high frequency sends; To be that positive half cycle or negative half period are permanent be high level to the control signal that sends to the switching tube that works in power frequency, and be low level square wave control signal in another half cycle perseverance.
Between first brachium pontis and second brachium pontis, also be connected with two sustained diode 7 and D8, its be connected to the ac output end of a brachium pontis in first brachium pontis and second brachium pontis and another brachium pontis two switching tubes that work in high frequency and power frequency respectively be connected in series a little between.Concrete, the anode of diode D7 is connected with interchange output point b, and being connected in series of negative electrode and switching tube VT1 and switching tube VT2 is connected, and as mentioned above, at the positive half cycle of line voltage, switching tube VT1 is operated in high frequency, and switching tube VT2 is operated in power frequency; Being connected in series of the anode of diode D8 and switching tube VT3 and switching tube VT4 is connected, negative electrode with exchange output point b and be connected, as mentioned above, at the line voltage negative half period, switching tube VT3 is operated in power frequency, switching tube VT4 is operated in high frequency.
The effect of sustained diode 7 is, at the positive half cycle of line voltage, when the switching tube VT1 that is operated in high frequency and VT6 by, the switching tube VT2 that is operated in power frequency still during conducting (, when the SPWM modulation signal that sends to switching tube VT1 and VT6 is in low level, when the square-wave signal that sends to switching tube VT2 is high level), form continuous current circuit with the switching tube VT2 that is operated in power frequency.The effect of sustained diode 8 is, at the line voltage negative half period, when the switching tube VT5 that is operated in high frequency and VT4 by, the switching tube VT3 that is operated in power frequency still during conducting (, when the SPWM modulation signal that sends to switching tube VT5 and VT4 is in low level, when the square-wave signal that sends to switching tube VT3 is high level), form continuous current circuit with the switching tube VT3 that is operated in power frequency.
Fig. 6 is the control signal sequential chart of embodiment 1 each switching tube, i.e. the order of each switching tube gate portion bit motion and the retention time of each state, the action of each switching tube is determined by the control signal sequential.In Fig. 6, control signal 1 is identical high frequency bipolar SPWM drive waveforms with control signal 6 at the positive half cycle of line voltage (during 0~0.5T), and negative half period (during 0.5T~T) is a low level; Control signal 2 is a high level at the positive half cycle of line voltage, and negative half period is a low level; Control signal 3 is a low level at the positive half cycle of line voltage, and negative half period is a high level; Control signal 4 and control signal 5 are low level at the positive half cycle of line voltage, and negative half period is consistent with control signal 1 positive half cycle.
Fig. 2~Fig. 5 is operated in the fundamental diagram in a line voltage cycle for each switching tube of embodiment 1 full-bridge circuit, correspondingly conducting or end of the control signal that each switching tube of full-bridge circuit sends according to control circuit, the direct current Vin that the photovoltaic array of full-bridge circuit input is produced converts alternating current to, exports the feed-in electrical network then.Fig. 2~Fig. 5 is analyzed the respective action of sequential and each switching tube below in conjunction with Fig. 6.
Fig. 2 is the fundamental diagram of embodiment 1 circuit when the positive half cycle of line voltage.As shown in Figure 2, at the positive half cycle of line voltage, control signal 2 control switch pipe VT2 normal opens, switching tube VT2 works in power frequency; Control signal 3 control switch pipe VT3 end; Control signal 1 works in high frequency with control signal 6 with identical FREQUENCY CONTROL switching tube VT1 and VT6; Control signal 4 and control signal 5 control switch pipe VT4 and VT5 end.As the switching tube VT1, the VT6 that are operated in high frequency with when being operated in the switching tube VT2 conducting of power frequency, the sense of current in the circuit as shown in phantom in Figure 2.
Fig. 3 is the fundamental diagram of embodiment 1 continuous current circuit when the positive half cycle of line voltage.As shown in Figure 3, at the positive half cycle of line voltage, when the switching tube VT1, the VT6 that are operated in high frequency end, when being operated in the switching tube VT2 conducting of power frequency, the sense of current in the circuit as shown in phantom in Figure 3, continuous current circuit thoroughly disconnects input side and electrical network.
Fig. 4 is the fundamental diagram of embodiment 1 circuit when the line voltage negative half period.As shown in Figure 4, at the line voltage negative half period, control signal 3 control switch pipe VT3 normal opens, VT3 works in power frequency; Control signal 2 control switch pipe VT2 end; Control signal 4 works in high frequency with control signal 5 with identical FREQUENCY CONTROL switching tube VT4 and VT5; Control signal 1 and control signal 6 control switch pipe VT1 and VT6 end.As the switching tube VT4, the VT5 that are operated in high frequency with when being operated in the switching tube VT3 conducting of power frequency, the sense of current in the circuit as shown in phantom in Figure 4.
Fig. 5 is the fundamental diagram of embodiment 1 continuous current circuit when the line voltage negative half period.As shown in Figure 5, at the line voltage negative half period, when the switching tube VT4, the VT5 that are operated in high frequency end, when being operated in the switching tube VT3 conducting of power frequency, the sense of current in the circuit as shown in phantom in Figure 5, continuous current circuit thoroughly disconnects input side and electrical network.
As seen, under the driving of each control signal of control circuit, be operated in the switching tube modulation output half-sinusoid voltage of high frequency in the full-bridge circuit, the switching tube that is operated in power frequency makes the half-sinusoid voltage of output form the positive half cycle or the negative half period of line voltage.Through the conducting of each switching tube of full-bridge circuit or end, the direct current that photovoltaic array produces is converted to and the same amplitude of line voltage, with frequently, the alternating current of homophase, and feed-in electrical network Grid.Simultaneously, positive half cycle or negative half period at line voltage, when control circuit is low level to synchronous working in the SPWM modulator control signal of the switching tube transmission of high frequency, and when the control signal perseverance that the switching tube that works in power frequency sends was high level, the switching tube that works in power frequency of fly-wheel diode and conducting formed continuous current circuit between two ac output ends.
Here; should be appreciated that; control signal of the present invention is not limited to above-mentioned SPWM modulator control signal and square wave control signal, anyly makes full-bridge circuit provided by the present invention all should be included in protection scope of the present invention according to the control signal of above-mentioned working method work.
Fig. 7 and Fig. 8 are respectively the topology diagrams of photovoltaic combining inverter embodiment 2 of the present invention and embodiment 3, its first brachium pontis and second brachium pontis comprise three switching tubes that have the reverse parallel connection diode that are connected in series respectively, and the ac output end of first brachium pontis and second brachium pontis lays respectively at being connected in series a little of a switching tube in first brachium pontis and second brachium pontis and two other switching tube.
As shown in Figure 7, this topological structure is with switching tube VT3, VT4 and VT5 reversing of position on the basis of the topological structure of embodiment 1, thereby VT1, VT2, VT5 on first brachium pontis are connected successively, diode D1, D2, D5 respectively with switching tube VT1, VT2, VT5 reverse parallel connection; Switching tube VT4, VT3 on second brachium pontis, VT6 connect successively, diode D4, D3, D6 respectively with switching tube VT4, VT3, VT6 reverse parallel connection.Being connected in series of the switching tube VT2 of first brachium pontis and VT5 a little is ac output end a, and being connected in series of the switching tube VT3 of second brachium pontis and VT6 a little is ac output end b.The anode of sustained diode 8 is connected with the ac output end a point of first brachium pontis, and being connected in series of negative electrode and switching tube VT4 and VT3 is connected; The anode of sustained diode 7 is connected with the ac output end b point of second brachium pontis, and being connected in series of negative electrode and switching tube VT1 and VT2 is connected.Be connected with electrical network Grid with L2 by output inductor L1 between ac output end a and the ac output end b.The working method of the topological structure after the conversion is identical with embodiment 1 with continuous current circuit.
Control mode among the embodiment 2 is also all identical with embodiment 1 with the control signal sequential chart, and at the positive half cycle of line voltage, switching tube VT2 normal open works in work frequency; Switching tube VT1 and VT6 synchronous working are in the high frequency frequency; Switching tube VT3, VT4 and VT5 end.As the switching tube VT1, the VT6 that are operated in high frequency with when being operated in the switching tube VT2 conducting of power frequency, the electric current in the circuit flow through successively switching tube VT1, VT2, L1, L2, VT6.The path of continuous current circuit is when the positive half cycle of line voltage: at the positive half cycle of line voltage, when the switching tube VT1, the VT6 that are operated in high frequency end, when being operated in the switching tube VT2 conducting of power frequency, flow through successively VT2, L1, L2, D7, VT2 of the electric current in the circuit forms continuous current circuit.
At the line voltage negative half period, switching tube VT3 normal open works in work frequency; Switching tube VT4 and VT5 synchronous working are in the high frequency frequency; Switching tube VT1, VT2 and VT6 end.As the switching tube VT4, the VT5 that are operated in high frequency with when being operated in the switching tube VT3 conducting of power frequency, the electric current in the circuit flow through successively switching tube VT4, VT3, L2, L1, VT5.The path of continuous current circuit is when the line voltage negative half period: at the line voltage negative half period, when the switching tube VT4, the VT5 that are operated in high frequency end, when being operated in the switching tube VT3 conducting of power frequency, flow through successively VT3, L2, L1, D8, VT3 of the electric current in the circuit forms continuous current circuit.
As shown in Figure 8, this topological structure is with switching tube VT1, VT2 and VT6 reversing of position on the basis of the topological structure of embodiment 1, thereby switching tube VT6, VT3, VT4 on first brachium pontis are connected successively, diode D6, D3, D4 respectively with switching tube VT6, VT3, VT4 reverse parallel connection; VT5 on second brachium pontis, VT2, VT1 connect successively, diode D5, D2, D1 respectively with switching tube VT5, VT2, VT1 reverse parallel connection.Being connected in series of the switching tube VT6 of first brachium pontis and VT3 a little is ac output end a, and being connected in series of the switching tube VT5 of second brachium pontis and VT2 a little is ac output end b.The anode of sustained diode 8 a little is connected with switching tube VT3 and being connected in series of VT4, and negative electrode is connected with the ac output end b point of second brachium pontis; The anode of sustained diode 7 a little is connected with switching tube VT1 and being connected in series of VT2, and negative electrode is connected with the ac output end a point of first brachium pontis.Be connected with electrical network Grid with L2 by output inductor L1 between ac output end a and the ac output end b.The working method of the topological structure after the conversion is identical with embodiment 1 with continuous current circuit.
Control mode among the embodiment 3 is also all identical with embodiment 1 with the control signal sequential chart, and at the positive half cycle of line voltage, switching tube VT2 normal open works in work frequency; Switching tube VT1 and VT6 synchronous working are in the high frequency frequency; Switching tube VT3, VT4 and VT5 end.As the switching tube VT1, the VT6 that are operated in high frequency with when being operated in the switching tube VT2 conducting of power frequency, the electric current in the circuit flow through successively switching tube VT6, L1, L2, VT2, VT1.The path of continuous current circuit is when the positive half cycle of line voltage: at the positive half cycle of line voltage, when the switching tube VT1, the VT6 that are operated in high frequency end, when being operated in the switching tube VT2 conducting of power frequency, flow through successively VT2, D7, L1, L2, VT2 of the electric current in the circuit forms continuous current circuit.
At the line voltage negative half period, switching tube VT3 normal open works in work frequency; Switching tube VT4 and VT5 synchronous working are in the high frequency frequency; Switching tube VT1, VT2 and VT6 end.As the switching tube VT4, the VT5 that are operated in high frequency with when being operated in the switching tube VT3 conducting of power frequency, the electric current in the circuit flow through successively switching tube VT5, L2, L1, VT3, VT4.The path of continuous current circuit is when the line voltage negative half period: at the line voltage negative half period, when the switching tube VT4, the VT5 that are operated in high frequency end, when being operated in the switching tube VT3 conducting of power frequency, flow through successively VT3, D8, L2, L1, VT3 of the electric current in the circuit forms continuous current circuit.
More than topological structure and control method among 3 embodiment, the common-mode voltage range of AC side output is identical with the common-mode voltage range of the interchange output of unipolarity modulation, the current potential that is continuous current circuit is between 0~0.5Vin, therefore common-mode voltage and consequent common mode current in the single-phase non-isolation type photovoltaic combining inverter have been effectively reduced, switching tube loss simultaneously is reduced, and has also therefore improved the transformation of electrical energy efficient of inverter; And directly be connected owing to the switching tube that is operated in high frequency exists with negative pole with the positive pole of direct current input side, when the switching tube that is operated in high frequency ended, continuous current circuit and direct current input side thoroughly disconnected, thereby reached the purpose that suppresses common mode current better.
Be understandable that above execution mode only is the illustrative embodiments that adopts for principle of the present invention is described, yet the present invention is not limited thereto.For those skilled in the art, without departing from the spirit and substance in the present invention, can make various modification and improvement, these modification and improvement also are considered as protection scope of the present invention.

Claims (8)

1. single-phase non-isolation type photovoltaic combining inverter comprises:
Full-bridge circuit, it is used for the direct voltage that photovoltaic array produces is converted to the sine voltage that satisfies the needs that are incorporated into the power networks, comprise first brachium pontis and second brachium pontis, first brachium pontis is provided with two or three or four switching tubes that have the reverse parallel connection diode that are connected in series, correspondingly be provided with four or three or two switching tubes that have the reverse parallel connection diode that are connected in series on second brachium pontis, and, first brachium pontis and second brachium pontis are in parallel with input DC power respectively, and the ac output end of first brachium pontis and second brachium pontis is connected to the network access filter inductance respectively;
Control circuit, it is used for respectively transmitting control signal to each switching tube of first brachium pontis and second brachium pontis, so that the switching tube conducting in the following manner in first brachium pontis and second brachium pontis or end: at positive half cycle of line voltage or negative half period, have three switching tube conductings on first brachium pontis and second brachium pontis, so that electric current flows to negative pole from the input DC power positive pole, described three switching tubes comprise one or two switching tube and the ac output end that is connected this brachium pontis of another brachium pontis and two or the switching tube between the input DC power negative pole between the ac output end that is connected anodal and this brachium pontis of input DC power of a brachium pontis in first brachium pontis and second brachium pontis, and be operated in high frequency successively according to order from the input DC power positive pole to negative pole, power frequency and high frequency, rest switch pipe in the win brachium pontis and second brachium pontis is ended, wherein, the described switching tube that is operated in high frequency is used for modulation output half-sinusoid voltage, and the described switching tube that is operated in power frequency is used to make the half-sinusoid voltage of the switching tube output that is operated in high frequency to form the positive half cycle or the negative half period of line voltage;
Two fly-wheel diodes, its be connected to the ac output end of a brachium pontis in first brachium pontis and second brachium pontis and another brachium pontis two switching tubes that work in high frequency and power frequency respectively be connected in series a little between, be used for when the switching tube that is operated in high frequency by the time form continuous current circuit with the switching tube that is operated in power frequency.
2. single-phase non-isolation type photovoltaic combining inverter according to claim 1 is characterized in that described switching tube is mos field effect transistor or insulated gate bipolar transistor.
3. single-phase non-isolation type photovoltaic combining inverter according to claim 1 is characterized in that, described control circuit adopts the DSP microprocessor.
4. single-phase non-isolation type photovoltaic combining inverter according to claim 1 is characterized in that, described control circuit is a high frequency SPWM modulator control signal to the control signal that the switching tube that works in high frequency sends.
5. single-phase non-isolation type photovoltaic combining inverter according to claim 1, it is characterized in that, to be that positive half cycle or negative half period are permanent be high level to the control signal that described control circuit sends to the switching tube that works in power frequency, and be low level square wave control signal in another half cycle perseverance.
6. the control method of a single-phase non-isolation type photovoltaic combining inverter, described photovoltaic combining inverter comprises full-bridge circuit and two fly-wheel diodes, wherein, described full-bridge circuit comprises first brachium pontis and second brachium pontis, first brachium pontis is provided with two or three or four switching tubes that have the reverse parallel connection diode that are connected in series, correspondingly be provided with four or three or two switching tubes that have the reverse parallel connection diode that are connected in series on second brachium pontis, and first brachium pontis and second brachium pontis are in parallel with input DC power respectively, the ac output end of first brachium pontis and second brachium pontis is connected to the network access filter inductance respectively, described two fly-wheel diodes be connected to the ac output end of a brachium pontis in first brachium pontis and second brachium pontis and another brachium pontis two switching tubes that work in high frequency and power frequency respectively be connected in series a little between, described method comprises:
Each switching tube in first brachium pontis and second brachium pontis transmits control signal respectively, so that the switching tube conducting in the following manner in first brachium pontis and second brachium pontis or end: at positive half cycle of line voltage or negative half period, have three switching tube conductings on first brachium pontis and second brachium pontis, so that electric current flows to negative pole from the input DC power positive pole, described three switching tubes comprise one or two switching tube and the ac output end that is connected this brachium pontis of another brachium pontis and two or the switching tube between the input DC power negative pole between the ac output end that is connected anodal and this brachium pontis of input DC power of a brachium pontis in first brachium pontis and second brachium pontis, and be operated in high frequency successively according to order from the input DC power positive pole to negative pole, power frequency and high frequency, rest switch pipe in the win brachium pontis and second brachium pontis is ended, wherein, the described switching tube that is operated in high frequency is used for modulation output half-sinusoid voltage, and the described switching tube that is operated in power frequency is used to make the half-sinusoid voltage of the switching tube output that is operated in high frequency to form the positive half cycle or the negative half period of line voltage.
7. method according to claim 6 is characterized in that, described control circuit is a high frequency SPWM modulator control signal to the control signal that the switching tube that works in high frequency sends.
8. method according to claim 6 is characterized in that, to be that positive half cycle or negative half period are permanent be high level to the control signal that described control circuit sends to the switching tube that works in power frequency, and is low level square wave control signal in another half cycle perseverance.
CN2011100475384A 2011-02-28 2011-02-28 Single-phase non-isolation type photovoltaic grid-connected inverter and control method CN102157955A (en)

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CN105553321A (en) * 2016-01-20 2016-05-04 南昌航空大学 Switch tube clamping type transformerless photovoltaic inverter topology
CN105743382A (en) * 2016-03-11 2016-07-06 苏州爱科博瑞电源技术有限责任公司 DC-AC conversion device and inverter based on same

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102088193A (en) * 2011-03-04 2011-06-08 东南大学 Photovoltaic synchronization grid full bridge six-switching tube inverter and control method thereof
CN102255546A (en) * 2011-07-29 2011-11-23 阳光电源股份有限公司 Inverter
CN102291032A (en) * 2011-07-29 2011-12-21 阳光电源股份有限公司 Inverter
CN102291027A (en) * 2011-08-19 2011-12-21 阳光电源股份有限公司 Inverter
CN102403921A (en) * 2011-12-01 2012-04-04 合肥索维能源科技有限公司 High-efficiency inverter with low output leakage current
CN102780412A (en) * 2012-06-29 2012-11-14 阳光电源(上海)有限公司 Single-phase half-bridge three-level circuit and inverter
CN102780412B (en) * 2012-06-29 2015-02-18 阳光电源(上海)有限公司 Single-phase half-bridge three-level circuit and inverter
CN102904279A (en) * 2012-09-29 2013-01-30 西安龙腾新能源科技发展有限公司 Inverter circuit topology and control method thereof
CN103051224A (en) * 2012-12-24 2013-04-17 江苏兆伏新能源有限公司 Reactive power control method of contravariant topology circuit
CN103051224B (en) * 2012-12-24 2015-03-04 江苏兆伏新能源有限公司 Reactive power control method of contravariant topology circuit
CN105553321A (en) * 2016-01-20 2016-05-04 南昌航空大学 Switch tube clamping type transformerless photovoltaic inverter topology
CN105743382A (en) * 2016-03-11 2016-07-06 苏州爱科博瑞电源技术有限责任公司 DC-AC conversion device and inverter based on same

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Application publication date: 20110817