CN102710133A

CN102710133A - Seven-level circuit, a grid-connected inverter and modulation method and device of seven-level circuit

Info

Publication number: CN102710133A
Application number: CN2012101926287A
Authority: CN
Inventors: 汪洪亮; 赵为
Original assignee: Sungrow Power Supply Co Ltd
Current assignee: Hefei Solar Power Supply Information Technology Co., Ltd.
Priority date: 2012-06-12
Filing date: 2012-06-12
Publication date: 2012-10-03
Anticipated expiration: 2032-06-12
Also published as: CN102710133B

Abstract

The invention relates to a seven-level circuit, a grid-connected inverter and a modulation method and device of the seven-level circuit. The seven-level circuit comprises a DC boosted circuit and a symmetric dual-Buck circuit; the DC boosted circuit comprises a DC chopper and a fourth capacitor which are connected in series; an eighth switching tube is connected between the common terminal of the DC chopper and the fourth capacitor and the common terminal of a first switching tube and a first diode; the symmetric dual-Buck circuit comprises the following structures that a first capacitor and a second capacitor are connected in series and then connected to two sides of a DC power supply in parallel, the first diode and a second diode are connected in series and then connected with the DC power supply in parallel, the first switching tube is arranged between the first capacitor and the second diode, and a second switching tube is arranged between the second diode and the second capacitor; a first inductor is arranged between the first diode and the output end of the seven-level circuit, and a second inductor is arranged between the common terminal of the second switching tube and the second diode and the output end of the seven-level circuit; and a common point of the first capacitor and the second capacitor is connected with a common point of the first diode and the second diode. The seven-level circuit, the grid-connected inverter and a control method and device of the grid-connected inverter give consideration to two aspects of current and high efficiency.

Description

A kind of seven level circuits, combining inverter and modulator approach and device

Technical field

The present invention relates to electric and electronic technical field, particularly a kind of seven level circuits, combining inverter and modulator approach and device.

Background technology

The classification of inverter; Generally be to be divided into from net type inverter and grid type inverter according to the different of inverter applications occasion and control mode, whether basis has transformer and can be divided into transformer isolation type inverter and transless type inverter again in the grid type inverter.

Plurality of advantages such as transless type inverter is simple owing to system configuration, and efficient is high, and volume is little, and cost is low have obtained development fast.

But transless type inverter is owing to can not realize the electrical isolation between direct current input source and AC load, and leakage problem is one of key index of its reliability.

For obtaining higher efficient, often adopt the unipolarity modulation strategy, traditional H4 topology can not be taken into account leakage current and high efficiency simultaneously.Be to eliminate the high frequency common mode voltage that the Unipolar SPWM modulation produces, must make just can reach the purpose of eliminating the common-mode voltage leakage current by clamped half the at solar array voltage of the continuous current circuit in afterflow stage.Employing modified model topology like H5, H6, Heric topology, has realized the unipolarity modulation strategy, has solved leakage problem to a certain extent, and its brachium pontis output voltage equivalence is the outputs of three level.

Summary of the invention

The technical problem that the present invention will solve provides a kind of seven level and combining inverter and modulator approach and system, realizes taking into account the problem of leakage current and high efficiency two aspects.

The present invention provides a kind of seven level circuits, the symmetric double Buck circuit that said seven level circuits comprise DC voltage booster circuit, are in parallel with DC power supply;

Said DC voltage booster circuit comprises: DC chopper and the 4th capacitor C B1 series connection, and the negative busbar end of DC power supply links to each other the positive bus-bar end connection DC chopper of DC power supply with the 4th capacitor C B1;

Be connected with the 8th switching tube between the common port of the common port of said DC chopper and the 4th capacitor C B1 and first switching tube and first diode;

Said symmetric double Buck circuit comprises: be connected in parallel on said DC power supply both sides after first electric capacity and second capacitances in series; First diode and second diode series connection back are parallelly connected with said DC power supply; Be provided with first switching tube between first electric capacity and first diode, be provided with the second switch pipe between second diode and second electric capacity; Be provided with first inductance between the common port of first diode and first switching tube and the said seven level circuit outputs, be provided with second inductance between the common port of the second switch pipe and second diode and the said seven level circuit outputs; First electric capacity directly links to each other with the tie point of first diode with second diode with the tie point of second electric capacity.

Preferably, said DC chopper comprises: the 5th inductance and the 3rd diode of connecting between the positive bus-bar end of DC power supply and said the 4th capacitor C B1; The 7th switching tube that is provided with between the negative busbar end of the common port of the 5th inductance and the 3rd diode and DC power supply.

Preferably, comprising:

Control the on off state of said first switching tube, second switch pipe and the 8th switching tube, the voltage that makes the common port of the win electric capacity and second electric capacity is the half the of DC power supply output voltage V 1; The output voltage V 3 of said seven level circuits is the absolute value of line voltage;

Make that the output voltage V 3 of said seven level circuits is the waveform of line voltage peak value for sinuous pulsation, peak value with cycle T and continuous two positive half cycles, said cycle T is the line voltage cycle.

The present invention also provides a kind of modulator approach of seven level circuits, comprising:

When the DC power supply output voltage was higher than the peak value of modulating wave, said DC voltage booster circuit was not worked, and controlled turning on and off of first and second switching tube, made said seven level circuits work according to five level adjustment modes;

Said modulating wave has three zero crossings in one-period T, be designated as t respectively ₀, t ₄And t ₈t ₄Mid point for cycle T; Obtain this three zero crossing t ₀, t ₄And t ₈

With t ₀Postpone 1/4 mid point t that cycle T then was first half period ₂With t ₀Postpone 3/4 mid point t that cycle T then was second half period ₆

The straight line that the waveform of first half period of said modulating wave and the waveform of second half period are corresponding with V1/2 respectively has two intersection points, is respectively t ₁And t ₃, and t ₅And t ₇

t ₀-t ₁Time period, to control first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control second switch pipe turn-offs;

t ₁-t ₂Time period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe;

t ₂-t ₃Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting;

t ₃-t ₄Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off;

t ₄-t ₅Time period, control said first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said second switch pipe and turn-off;

t ₅-t ₆Time period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe;

t ₆-t ₇Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting;

t ₇-t ₈Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off.

Preferably,

When the DC power supply output voltage is higher than the peak value of modulating wave, said DC voltage booster circuit work, control first and second, the turning on and off of eight switching tubes, make said seven level circuits work according to seven level adjustment modes;

Modulating wave has three zero crossings in one-period T, be designated as t respectively ₀, t ₄And t ₈t ₄Mid point for cycle T; Obtain this three zero crossing t ₀, t ₄And t ₈

The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1/2 respectively has two intersection points, is designated as t respectively ₁And t ₃, and t ₅And t ₇

At time point t ₁And t ₂Between time point t is set _1x, at time point t ₂And t ₃Between time point t is set _3x, time point t _1xWith time point t _3xWith time point t ₂Be the center;

At time point t ₅And t ₆Between time point t is set _5x, at time point t ₆And t ₇Between time point t is set _7x, time point t _5xWith time point t _7xWith time point t ₂Be the center; And t _1x-t _3xTime period equals t _5x-t _7xTime period;

t ₀-t ₁Time period, to control first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control second switch pipe turn-offs, and controls the 8th switching tube and turn-offs;

t ₁-t _1xTime period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe, control the 8th switching tube and turn-off;

t _1x-t _3xTime period, control the conducting of said second switch pipe, control first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube turn-offs and conducting according to the sinusoid pulse width modulation modulation;

t _3x-t ₃Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting, control the 8th switching tube and turn-off;

t ₃-t ₄Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off, control the 8th switching tube and turn-off;

t ₄-t ₅Time period, control said first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said second switch pipe and turn-off, control the 8th switching tube and turn-off;

t ₅-t _5xTime period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe, control the 8th switching tube and turn-off;

t _5x-t _7xTime period, control the conducting of said second switch pipe, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube turn-offs and conducting according to the sinusoid pulse width modulation modulation;

t _7x-t ₇Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting, control the 8th switching tube and turn-off;

t ₇-t ₈Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off, control the 8th switching tube and turn-off.

Preferably,

When the DC power supply output voltage is lower than the peak value of modulating wave, said DC voltage booster circuit work, control first and second, the turning on and off of eight switching tubes, make said seven level circuits work according to seven level adjustment modes;

The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1 respectively has two intersection points, is designated as t respectively _1yAnd t _3y, and t _5yAnd t _7y

t ₀-t ₁Time period, to control first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control second switch pipe turn-offs, and the 8th switching tube in the control DC voltage booster circuit turn-offs;

t ₁-t _1yTime period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe, control the 8th switching tube and turn-off;

t _1y-t _3yTime period, control the conducting of said second switch pipe, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube turn-offs and conducting according to the sinusoid pulse width modulation modulation;

t _3y-t ₃Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting, control the 8th switching tube and turn-off;

t ₅-t _5yTime period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe, control the 8th switching tube and turn-off;

t _5y-t _7yTime period, control the conducting of said second switch pipe, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube turn-offs and conducting according to the sinusoid pulse width modulation modulation;

t _7y-t ₇Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting, control the 8th switching tube and turn-off;

The present invention also provides a kind of modulating device of seven level circuits; Said modulating device is through the on off state of control said first switching tube, second switch pipe and the 8th switching tube, and the voltage that makes the common port of the win electric capacity and second electric capacity is the half the of DC power supply output voltage V 1; The output voltage V 3 of said seven level circuits is the absolute value of line voltage.

Preferably, comprising: first switch tube working status confirms that unit, the very first time confirm the unit and first control unit;

Said first switch tube working status is confirmed the unit; Be used for when the DC power supply output voltage is higher than the amplitude of modulating wave; Said DC voltage booster circuit is not worked, and controls turning on and off of first and second switching tube, makes said seven level circuits work according to five level adjustment modes;

The said very first time is confirmed the unit, is used for confirming the time period of modulation; Be specially: modulating wave has three zero crossings in one-period T, be designated as t respectively ₀, t ₄And t ₈t ₄Mid point for cycle T; Obtain this three zero crossing t ₀, t ₄And t ₈With t ₀Postpone 1/4 mid point t that cycle T then was first half period ₂With t ₀Postpone 3/4 mid point t that cycle T then was second half period ₆The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1/2 respectively has two intersection points, is designated as t respectively ₁And t ₃, and t ₅And t ₇

Said first control unit is used to control the on off state of first switching tube and second switch pipe, is specially: t ₀-t ₁Time period, to control first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control second switch pipe turn-offs; t ₁-t ₂Time period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe; t ₂-t ₃Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting; t ₃-t ₄Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off; t ₄-t ₅Time period, control said first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said second switch pipe and turn-off; t ₅-t ₆Time period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe; t ₆-t ₇Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting; t ₇-t ₈Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off.

Preferably, said device comprises: the second switch plumber makes status determining unit, second time and confirms the unit and second control unit;

Said second switch plumber makes status determining unit; Be used for when the DC power supply output voltage is higher than the peak value of modulating wave; Said DC voltage booster circuit work, control first and second, the turning on and off of eight switching tubes, make said seven level circuits work according to seven level adjustment modes;

Said second time is confirmed the unit, is used for confirming the time period of modulation; Be specially: modulating wave has three zero crossings in one-period T, be designated as t respectively ₀, t ₄And t ₈t ₄Mid point for cycle T; Obtain this three zero crossing t ₀, t ₄And t ₈With t ₀Postpone 1/4 mid point t that cycle T then was first half period ₂With t ₀Postpone 3/4 mid point t that cycle T then was second half period ₆The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1/2 respectively has two intersection points, is designated as t respectively ₁And t ₃, and t ₅And t ₇At time point t ₁And t ₂Between time point t is set _1x, at time point t ₂And t ₃Between time point t is set _3x, time point t _1xWith time point t _3xWith time point t ₂Be the center; At time point t ₅And t ₆Between time point t is set _5x, at time point t ₆And t ₇Between time point t is set _7x, time point t _5xWith time point t _7xWith time point t ₂Be the center; And t _1x-t _3xTime period equals t _5x-t _7xTime period; The voltage of the 4th capacitor C B1 is V2 in the said DC voltage booster circuit;

Said second control unit is used to control the on off state of first switching tube and second switch pipe and the 8th switching tube, is specially: t ₀-t ₁Time period, to control first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control second switch pipe and the 8th switching tube turn-off; t ₁-t ₂Time period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe, control the 8th switching tube and turn-off; t _1x-t _3xTime period, control the conducting of said second switch pipe, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube turn-offs and conducting according to the sinusoid pulse width modulation modulation; t _3x-t ₃Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting, control the 8th switching tube and turn-off; t ₃-t ₄Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off, control the 8th switching tube and turn-off; t ₄-t ₅Time period, control said first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said second switch pipe and turn-off, control the 8th switching tube and turn-off; t ₅-t _5xTime period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe, control the 8th switching tube and turn-off; t _5x-t _7xTime period, control the conducting of said second switch pipe, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube turn-offs and conducting according to the sinusoid pulse width modulation modulation; t _7x-t ₇Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting, control the 8th switching tube and turn-off; t ₇-t ₈Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off, control the 8th switching tube and turn-off.

Preferably, said device comprises: the 3rd switch tube working status confirms that unit, the 3rd time confirms unit and the 3rd control unit;

The 3rd switch tube working status is confirmed the unit; Be used for when the DC power supply output voltage is lower than the peak value of modulating wave; Said DC voltage booster circuit work, control first and second, the turning on and off of eight switching tubes, make said seven level circuits work according to seven level adjustment modes;

Said the 3rd time is confirmed the unit, is used for confirming the time period of modulation; Be specially: modulating wave has three zero crossings in one-period T, be designated as t respectively ₀, t ₄And t ₈t ₄Mid point for cycle T; Obtain this three zero crossing t ₀, t ₄And t ₈With t ₀Postpone 1/4 mid point t that cycle T then was first half period ₂With t ₀Postpone 3/4 mid point t that cycle T then was second half period ₆The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1/2 respectively has two intersection points, is designated as t respectively ₁And t ₃, and t ₅And t ₇The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1 respectively has two intersection points, is designated as t respectively _1yAnd t _3y, and t _5yAnd t _7yThe voltage of the 4th capacitor C B1 is V2 in the said DC voltage booster circuit;

Said the 3rd control unit is used to control the on off state of first switching tube and second switch pipe and the 8th switching tube, is specially: t ₀-t ₁Time period, to control first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control second switch pipe and the 8th switching tube turn-off; t ₁-t ₂Time period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe, control the 8th switching tube and turn-off; t _1y-t _3yTime period, control the conducting of said second switch pipe, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube turn-offs and conducting according to the sinusoid pulse width modulation modulation; t _3y-t ₃Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting, control the 8th switching tube and turn-off; t ₃-t ₄Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off, control the 8th switching tube and turn-off; t ₄-t ₅Time period, control said first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said second switch pipe and turn-off, control the 8th switching tube and turn-off; t ₅-t _5yTime period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe, control the 8th switching tube and turn-off; t _5y-t _7yTime period, control the conducting of said second switch pipe, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube turn-offs and conducting according to the sinusoid pulse width modulation modulation; t _7y-t ₇Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting, control the 8th switching tube and turn-off; t ₇-t ₈Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off, control the 8th switching tube and turn-off.

The present invention also provides a kind of combining inverter, comprises described seven level circuits, and the power frequency commutation inverter circuit parallelly connected with said seven level circuit outlet sides.

The present invention also provides a kind of combining inverter, comprises described seven level circuits, the power frequency commutation inverter circuit parallelly connected with said seven level circuit outlet sides, and between said seven level circuits and power frequency commutation inverter circuit, be parallel with the 3rd electric capacity.

The present invention also provides a kind of method of controlling combining inverter, and said combining inverter comprises described seven level circuits, and said seven level circuits adopt described modulator approach.

The present invention also provides a kind of device of controlling combining inverter, and said combining inverter comprises described seven level circuits, and said seven level circuits adopt described modulating device.

Compared with prior art, the present invention has the following advantages:

Said seven level circuits of the embodiment of the invention are because the symmetric double Buck circuit that circuit comprises DC voltage booster circuit, is in parallel with DC power supply; When said DC voltage booster circuit was worked, the seven level adjustment modes that can realize were worked.

When said seven level circuits of the embodiment of the invention are applied to combining inverter, can satisfy when prime DC power supply output voltage can not reach requiring of inverter voltage, through boosting of DC voltage booster circuit, thereby reach the requirement of inverter voltage, realize inversion.

The modulator approach of the said combining inverter of the embodiment of the invention and device; First half period and second half period at modulating wave are that the 3rd mode C and the 4th mode D appear in the compartment of terrain, the voltage fluctuation that produces on first capacitor C 1 of two Buck circuit and second capacitor C 2 in the time of can effectively offsetting the 3rd mode C and the 4th mode D like this.And continuous discharge and the lasting charging interval of first and second capacitor C 1, C2 and first and second inductance L 1, L2 are all shorter; Reduced the voltage undulation of first and second capacitor C 1, C2 and first and second inductance L 1, L2 greatly; Thereby reduce the ripple of output voltage, improved output waveform.And the modulator approach of the said combining inverter of the embodiment of the invention and device can be so that switching tube according to the regulative mode work of five level or seven level, have improved efficient.Increase owing to number of levels simultaneously, the voltage difference between the level reduces, the also corresponding minimizing of common-mode voltage, thus suppressed leakage current.

Description of drawings

Fig. 1 is that the present invention's seven level circuits are applied to the combining inverter first embodiment circuit diagram;

Fig. 2 is that the present invention's seven level circuits are applied to the combining inverter second embodiment circuit diagram;

Fig. 3 a is first kind of operation mode A sketch map of the embodiment of the invention seven level circuits;

Fig. 3 b is second kind of operation mode B sketch map of the embodiment of the invention seven level circuits;

Fig. 3 c is the third operation mode C sketch map of the embodiment of the invention seven level circuits;

Fig. 3 d is the 4th a kind of operation mode D sketch map of the embodiment of the invention seven level circuits;

Fig. 3 e is the 5th a kind of operation mode E sketch map of the embodiment of the invention seven level circuits;

Fig. 4 is the schematic diagram of modulator approach first embodiment of seven level circuits in the said combining inverter of the embodiment of the invention;

Fig. 5 is the schematic diagram of modulator approach second embodiment of seven level circuits in the said combining inverter of the embodiment of the invention;

Fig. 6 is the schematic diagram of modulator approach the 3rd embodiment of seven level circuits in the said combining inverter of the embodiment of the invention;

Fig. 7 is the structure chart of modulating device first embodiment of seven level circuits in the said combining inverter of the embodiment of the invention;

Fig. 8 is the structure chart of modulating device second embodiment of seven level circuits in the said combining inverter of the embodiment of the invention;

Fig. 9 is the structure chart of modulating device the 3rd embodiment of seven level circuits in the said combining inverter of the embodiment of the invention.

Embodiment

For make above-mentioned purpose of the present invention, feature and advantage can be more obviously understandable, does detailed explanation below in conjunction with the accompanying drawing specific embodiments of the invention.

Referring to Fig. 1, this is that the present invention's seven level circuits are applied to the combining inverter first embodiment circuit diagram.

A kind of seven level circuits, the symmetric double Buck circuit that comprises DC voltage booster circuit, is in parallel with DC power supply.

Be connected with the 8th switching tube TB2 between the common port of the common port of said DC chopper and the 4th capacitor C B1 and first switch transistor T 1 and the first diode D1.

Said symmetric double Buck circuit comprises: be connected in parallel on said DC power supply both sides after first capacitor C 1 and 2 series connection of second capacitor C; The first diode D1 and second diode D2 series connection back are parallelly connected with said DC power supply; Be provided with between first switch transistor T, 1, the second diode D2 and second capacitor C 2 between first capacitor C 1 and the first diode D1 and be provided with second switch pipe T2; Be provided with first inductance L 1 between the common port of the first diode D1 and first switch transistor T 1 and the seven level circuit outputs, be provided with second inductance L 2 between the common port of the second switch pipe T2 and the second diode D2 and the seven level circuit outputs; First electric capacity directly links to each other with the tie point of first diode with second diode with the tie point of second electric capacity.

Referring to Fig. 1, when said seven level circuits of the embodiment of the invention were applied to combining inverter, said inverter circuit comprised described seven level circuits, and the power frequency commutation inverter circuit that is in parallel with said seven level circuits.

When said seven level circuits of first embodiment of the invention are applied to combining inverter, can satisfy when the DC power supply output voltage can not reach requiring of inverter voltage, through boosting of DC voltage booster circuit, thereby reach the requirement of inverter voltage, realize inversion.

Between said seven level circuits and power frequency commutation inverter circuit, can also be parallel with the 3rd electric capacity, further reduce THD.

Referring to Fig. 2, this figure is that the present invention's seven level circuits are applied to the combining inverter second embodiment circuit diagram.

The difference of relative first embodiment of second embodiment of the invention is that said DC chopper provides concrete implementation.

Said DC chopper comprises: the 5th inductance L B1 and the 3rd diode DB1 that connect between the positive bus-bar end of DC power supply and said the 4th capacitor C B1; The 7th switching tube TB1 that is provided with between the common port of the 5th inductance L B1 and the 3rd diode DB1 and the negative busbar end of DC power supply.

Referring to Fig. 2, when said seven level circuits of the embodiment of the invention were applied to the photovoltaic inverter circuit, said inverter circuit comprised described seven level circuits, and the power frequency commutation inverter circuit that is in parallel with said seven level circuits.

When said seven level circuits of second embodiment of the invention are applied to the photovoltaic inverter circuit; Prime photovoltaic cell output voltage can satisfy when can not reach requiring of inverter voltage; Through boosting of DC voltage booster circuit; Make the magnitude of voltage that boosts of DC voltage booster circuit and the voltage sum of DC power supply reach the requirement of inverter voltage, thereby realize inversion.

Between said seven level circuits and power frequency commutation inverter circuit, can also be parallel with the 3rd capacitor C 3, further reduce THD.

The modulator approach of described seven level circuits of the embodiment of the invention comprises:

Control the on off state of said first switch transistor T 1, second switch pipe T2 and the 8th switch transistor T B2, the voltage that makes the common port of the win capacitor C 1 and second capacitor C 2 is the half the of DC power supply output voltage V 1; Make the output voltage V 3 of said seven level circuits be the absolute value of line voltage.

Referring to Fig. 3 a to Fig. 3 e, Fig. 3 a is the embodiment of the invention seven level circuits first kind of operation mode A sketch map of (also claiming two Buck circuit); Fig. 3 b is the embodiment of the invention seven level circuits second kind of operation mode B sketch map of (also claiming two Buck circuit); Fig. 3 c is the embodiment of the invention seven level circuits the third operation mode C sketch mapes of (also claiming two Buck circuit); Fig. 3 d is the embodiment of the invention seven level circuits the 4th kind of operation mode D sketch mapes of (also claiming two Buck circuit); Fig. 3 e is the 5th a kind of operation mode E sketch map of the embodiment of the invention seven level circuits.

First kind of operation mode A of the present invention's seven level circuits: first and second switch transistor T 1, T2 conducting simultaneously; The 8th switching tube TB2 turn-offs.

First and second capacitor C 1, C2 are electric simultaneously, and this moment, the 3rd capacitor C 3 voltages were DC power supply voltage V1, i.e. V3=V1.

Second kind of operation mode B of the present invention's seven level circuits: first and second, eight switching tube T1, T2, TB2 turn-off simultaneously; First and second inductance L 1, L2 are through first and second diode D1, D2 afterflow, and the 3rd capacitor C 3 voltages are 0, i.e. V3=0.

The third operation mode C of the present invention's seven level circuits: 1 conducting of first switch transistor T, second, eight switching tube T2, TB2 turn-off.First capacitor C 1 is an electric, and capacitor C 3 voltages are V1, i.e. V3=V1.

The 4th kind of operation mode state D of the present invention's seven level circuits: the first, eight switching tube T1, TB2 turn-off second switch pipe T2 conducting.Second capacitor C 2 is an electric, and the voltage of the 3rd capacitor C 3 is V1, i.e. V3=V1/2.

The 5th kind of operation mode state E of the present invention's seven level circuits: first switch transistor T 1 is turn-offed, second, eight switching tube T2, TB2 conducting simultaneously.The 4th capacitor C B1 is an electric, and the voltage of the 3rd capacitor C 3 is V2, i.e. V3=V2.

Referring to Fig. 4 is the schematic diagram of modulator approach first embodiment of seven level circuits in the said combining inverter of the embodiment of the invention.

The instantaneous value of absolute value of voltage of being incorporated into the power networks among Fig. 4 is u, and the instantaneous value of grid-connected current is i.Because modulating wave obtains after according to said line voltage sampling processing, said modulating wave waveform and said grid voltage waveform basically identical, difference can be ignored.Therefore adopt grid voltage waveform among the figure, can be considered to modulating wave.

The modulator approach of seven level circuits that present embodiment provides, the voltage of the common port of first capacitor C 1 and second capacitor C 2 are that half of direct voltage V1 is V1/2;

When the DC power supply output voltage was higher than the peak value of modulating wave, said DC voltage booster circuit was not worked, and first and second switch transistor T 1, T2 work according to five level adjustment modes.

When the present invention's seven level circuits are applied to photovoltaic combining inverter; Judge when photovoltaic PV voltage claims that also MPPT maximum power point tracking voltage (MPPT) is higher than the peak value of modulating wave; Said DC voltage booster circuit is not worked; First and second switch transistor T 1, T2 work according to five level adjustment modes, and the 3rd to the 6th switch transistor T 3, T4, T5, T6 play power frequency commutation effect work.

The voltage that is incorporated into the power networks has three zero crossings in one-period T, be designated as t0, t4 and t8 respectively; T4 is the mid point of cycle T; Obtain this three zero crossing t ₀, t ₄And t ₈

The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1/2 respectively has two intersection points, and two intersection point time corresponding of the straight line that the waveform of note first half period of modulating wave is corresponding with V1/2 are respectively t ₁And t ₃, two intersection point time corresponding of the straight line that the waveform of note second half period of modulating wave is corresponding with V1/2 are respectively t ₅And t ₇

t ₀-t ₁Time period, control first switch transistor T 1 and turn-off and conducting according to the sinusoid pulse width modulation modulation, control second switch pipe T2 turn-offs;

t ₁-t ₂Time period, control said first switch transistor T 1 according to sinusoid pulse width modulation modulation conducting and shutoff, control said second switch pipe T2 conducting;

t ₂-t ₃Time period, control said second switch pipe T2 according to sinusoid pulse width modulation modulation conducting and shutoff, control 1 conducting of said first switch transistor T;

t ₃-t ₄Time period, control said second switch pipe T2 and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switch transistor T 1 and turn-off;

t ₄-t ₅Time period, control said first switch transistor T 1 and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said second switch pipe T2 and turn-off;

t ₅-t ₆Time period, control said first switch transistor T 1 according to sinusoid pulse width modulation modulation conducting and shutoff, control said second switch pipe T2 conducting;

t ₆-t ₇Time period, control said second switch pipe T2 according to sinusoid pulse width modulation modulation conducting and shutoff, control 1 conducting of said first switch transistor T;

t ₇-t ₈Time period, control said second switch pipe T2 and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switch transistor T 1 and turn-off.

Need to prove; Switching tube conducting and shutoff discontinuously in the embodiment of the invention; Be to realize, for example, drive pulse signal be provided for the control end of first switch transistor T 1 by drive pulse signal; Then first switch transistor T, 1 conducting in the high level time section of drive pulse signal, then 1 shutoff of first switch transistor T in the low level time section of drive pulse signal.Conducting and the shutoff situation of second switch pipe T2 are similar.This drive pulse signal obtains according to the sinusoid pulse width modulation modulation.

Can find out t by Fig. 4 ₀-t ₁Time period, second kind of operation mode B of the present invention's seven level circuits and the third operation mode C of the present invention's seven level circuits switch;

t ₁-t ₂Time period, the 4th kind of operation mode D of first kind of operation mode A of the present invention's seven level circuits and the present invention's seven level circuits switches;

t ₂-t ₃Time period, first kind of operation mode A of the present invention's seven level circuits and the third operation mode C of the present invention's seven level circuits switch;

t ₃-t ₄Time period, the 4th kind of operation mode D of second kind of operation mode B of the present invention's seven level circuits and the present invention's seven level circuits switches;

t ₄-t ₅Time period, second kind of operation mode B of the present invention's seven level circuits and the third operation mode C of the present invention's seven level circuits switch;

t ₅-t ₆Time period, the 4th kind of operation mode D of first kind of operation mode A of the present invention's seven level circuits and the present invention's seven level circuits switches;

t ₆-t ₇Time period, first kind of operation mode A of the present invention's seven level circuits and the third operation mode C of the present invention's seven level circuits switch;

t ₇-t ₈Time period, the 4th kind of operation mode D of second kind of operation mode B of the present invention's seven level circuits and the present invention's seven level circuits switches.

As can beappreciated from fig. 4, the operation mode that switches in first half period of modulating wave is respectively BC, AD, AC and BD.Because circuit structure is symmetrical among first kind of operation mode A and the second kind of operation mode B; The state of first capacitor C 1, second capacitor C 2 is identical in first kind of operation mode A, discharge simultaneously, therefore; Can think that the voltage of DC power supply is constant during first kind of operation mode A; The mid point electric current of first capacitor C 1 and second capacitor C 2 is zero, and it is constant that the voltage of first capacitor C 1 and second capacitor C 2 keeps, and can not squint.

In second kind of operation mode B; The state of first capacitor C 1 and second capacitor C 2 also is identical; Do not discharge simultaneously, therefore, can think during second kind of operation mode B that the mid point electric current of first capacitor C 1 and second capacitor C 2 is zero; It is constant that the voltage of first capacitor C 1 and second capacitor C 2 keeps, and can not squint.Therefore, voltage is stable on first capacitor C 1 and second capacitor C 2 can not produce fluctuation.Therefore, in modulation, the voltage fluctuation in the time of can not considering first kind of operation mode A and second kind of operation mode B on first capacitor C 1 and second capacitor C 2.

During the third operation mode C, 1 discharge of first capacitor C, 2 chargings of second capacitor C.The voltage of such first capacitor C 1 and second capacitor C 2 squints.

During the 4th kind of operation mode D, 1 charging of first capacitor C, 2 discharges of second capacitor C.Like this, the voltage of first capacitor C 1 and second capacitor C 2 squints.

Voltage fluctuation when therefore, the embodiment of the invention is mainly considered the third operation mode C and the 4th kind of operation mode D on first capacitor C 1 and second capacitor C 2.In first half period of modulating wave, the operation mode that can regard switching as is: the third operation mode C, the 4th kind of operation mode D, the third operation mode C, the 4th kind of operation mode D.So just make the third operation mode C and the 4th kind of operation mode D compartment of terrain occur, thereby can offset the voltage fluctuation of generation on first capacitor C 1 and second capacitor C 2 among the third operation mode C and the 4th kind of operation mode D effectively.In like manner, the operation mode that switches in second half period of modulating wave also is the third operation mode of mode C, the 4th kind of operation mode D, the third operation mode C, the 4th kind of operation mode D.

Particularly, in first half period of modulating wave, t ₀-t ₁Time period the third operation mode C makes 1 discharge of first capacitor C, and voltage descends; t ₁-t ₂Time period the 4th kind of operation mode D makes 1 charging of first capacitor C, and voltage rises; t ₂-t ₃Time period, the third operation mode C makes 1 discharge of first capacitor C, and voltage descends; The t3-t4 time period, the 4th kind of operation mode D makes 1 charging of first capacitor C, and voltage rises.

The modulator approach of seven level circuits provided by the invention, the voltage fluctuation on first capacitor C 1 reduces significantly.Because similar on the fluctuation voltage on second capacitor C 2 and first capacitor C 1 repeated no more at this.

The modulator approach of seven level circuits that the embodiment of the invention provides; First half period and second half period at modulating wave are that the third operation mode C and the 4th kind of operation mode D appear in the compartment of terrain, the voltage fluctuation that produces on first capacitor C 1 and second capacitor C 2 in the time of can effectively offsetting the third operation mode C and the 4th kind of operation mode D like this.And the continuous discharge and the lasting charging interval of first capacitor C 1, second capacitor C 2 and first inductance L 1, second inductance L 2 are all shorter; Reduced the voltage undulation of first capacitor C 1, second capacitor C 2 and first inductance L 1, second inductance L 2 greatly; Thereby reduce the ripple of output voltage, improved output waveform.

Need to prove, obtain three the zero crossing ts of modulating wave at one-period T ₀, t ₄And t ₈A lot of implementations can be arranged, for example, can find out the moment of modulating wave zero crossing, obtain this three zero crossings through the phase-locked loop that is incorporated into the power networks.

Need to prove that said cycle T is by the mains frequency decision, for example, when mains frequency was 50Hz, said cycle T was 20ms.

Referring to Fig. 5, this figure is the schematic diagram of modulator approach second embodiment of seven level circuits in the said combining inverter of the embodiment of the invention.

When DC power supply output voltage (when being applied to photovoltaic combining inverter; Be photovoltaic PV voltage or MPPT maximum power point tracking voltage) when being higher than the peak value of modulating wave; Said DC voltage booster circuit work, first and second, eight switching tube T1, T2, TB2 can work according to seven level adjustment modes.

Fig. 5 in this case, DC power supply output voltage V 1 has reached the peak value of line voltage, but this moment, direct current boost booster circuit worked on, and makes the output voltage V 2 of DC voltage booster circuit greater than DC power supply output voltage V 1.

Wherein: when adopting modulator approach shown in Figure 5 for making, the efficient of seven level circuits is higher than the efficient that adopts modulator approach shown in Figure 4.

To t _1x, t _3x(t _1x-t _3xBe DC voltage booster circuit working hour) provided two design criterions and limited.

(1) under the situation that satisfies the THD requirement, as long as satisfy the DC voltage booster circuit output voltage V ₂Greater than the DC power supply output voltage V ₁, control V ₂Value is less as much as possible, to guarantee t _1x-t _3xAlthough time period DC voltage booster circuit work owing to increased a level modulation, all in all, can guarantee that still the efficient of seven level circuits is higher.

(2) under the situation that satisfies the THD requirement, t _1xValue is more a little bit smaller as much as possible, to guarantee from the V1/2 level to V ₁The switching time of level with from V ₁Level is to V ₂The switching time of level is basic identical, and the whole like this cycle gets off, and can guarantee that still the efficient of seven level circuits is higher.

In sum, when adopting modulator approach shown in Figure 5, can realize seven level, so efficient is higher than the efficient that adopts modulator approach shown in Figure 4.

The voltage of first electric capacity in the present invention's seven level circuits and the common port of second electric capacity is that half of direct voltage V1 is V1/2; The voltage of the 4th capacitor C B1 is V2 in the said DC voltage booster circuit;

The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1/2 respectively has two intersection points, and two intersection point time corresponding of the straight line that the waveform of first half period of modulating wave is corresponding with V1/2 are designated as t respectively ₁And t ₃, two intersection point time corresponding of the straight line that the waveform of second half period of modulating wave is corresponding with V1/2 are designated as t respectively ₅And t ₇

At time point t ₁And t ₂Between time point t is set _1x, at time point t ₂And t ₃Between time point t is set _2x, time point t _1xWith time point t _2xWith time point t ₂Be the center;

At time point t ₅And t ₆Between time point t is set _5x, at time point t ₆And t ₇Between time point t is set _7x, time point t _5xWith time point t _7xWith time point t ₂Be the center; And t _1x-t _2xTime period equals t _5x-t _7xTime period;

t ₀-t ₁Time period, control first switch transistor T 1 and turn-off and conducting according to the sinusoid pulse width modulation modulation, control second switch pipe T2 turn-offs, and the 8th switching tube TB2 in the control DC voltage booster circuit turn-offs;

t ₁-t _1xTime period, control said first switch transistor T 1 according to sinusoid pulse width modulation modulation conducting and shutoff, control said second switch pipe T2 conducting, control the 8th switching tube TB2 and turn-off;

t _1x-t _2xTime period, control the conducting of said second switch pipe, control said first switch transistor T 1, T2 according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube TB2 turn-offs and conducting according to the sinusoid pulse width modulation modulation;

t _2x-t ₃Time period, control said second switch pipe T2 according to sinusoid pulse width modulation modulation conducting and shutoff, control 1 conducting of said first switch transistor T, control the 8th switching tube TB2 and turn-off;

t ₃-t ₄Time period, control said second switch pipe T2 and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switch transistor T 1 and turn-off, control the 8th switching tube TB2 and turn-off;

t ₄-t ₅Time period, control said first switch transistor T 1 and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said second switch pipe T2 and turn-off, control the 8th switching tube TB2 and turn-off;

t ₅-t _5xTime period, control said first switch transistor T 1 according to sinusoid pulse width modulation modulation conducting and shutoff, control said second switch pipe T2 conducting, control the 8th switching tube TB2 and turn-off;

t _5x-t _7xTime period, control the conducting of said second switch pipe, control said first switch transistor T 1, T2 according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube TB2 turn-offs and conducting according to the sinusoid pulse width modulation modulation;

t _7x-t ₇Time period, control said second switch pipe T2 according to sinusoid pulse width modulation modulation conducting and shutoff, control 1 conducting of said first switch transistor T, control the 8th switching tube TB2 and turn-off;

t ₇-t ₈Time period, control said second switch pipe T2 and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switch transistor T 1 and turn-off, control the 8th switching tube TB2 and turn-off.

Can find out t by Fig. 5 ₀-t ₁Time period, second kind of operation mode B and the third operation mode C switch;

t ₁-t _1xTime period, first kind of operation mode A and the 4th kind of operation mode D switch;

t _1x-t _2xTime period, first kind of operation mode A and the 5th kind of operation mode E switch;

t _2x-t ₃Time period, first kind of operation mode A and the third operation mode C switch;

t ₃-t ₄Time period, second kind of operation mode B and the 4th kind of operation mode D switch;

t ₄-t ₅Time period, second kind of operation mode B and the third operation mode C switch;

t ₅-t _5xTime period, first kind of operation mode A and the 4th kind of operation mode D switch;

t _5x-t _7xTime period, first kind of operation mode A and the 5th kind of operation mode E switch;

t _7x-t ₇Time period, first kind of operation mode A and the third operation mode C switch;

t ₇-t ₈Time period, second kind of operation mode B and the 4th kind of operation mode D switch.

Referring to Fig. 6, this figure is the schematic diagram of modulator approach the 3rd embodiment of seven level circuits in the combining inverter of the present invention.

When the DC power supply output voltage (when being applied to photovoltaic combining inverter; Be photovoltaic PV voltage or MPPT maximum power point tracking voltage) when being lower than the peak value of modulating wave; Said DC voltage booster circuit work; Control first and second, the turning on and off of eight switching tube T1, T2, TB2, make said seven level circuits work according to seven level adjustment modes;

The voltage of first capacitor C 1 in the present invention's seven level circuits and the common port of second capacitor C 2 is that half of direct voltage V1 is V1/2; The voltage of the 4th capacitor C B1 is V2 in the said DC voltage booster circuit;

The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1 respectively has two intersection points, and two intersection point time corresponding of the straight line that the waveform of first half period of modulating wave is corresponding with V1 are designated as t respectively _1yAnd t _3y, two intersection point time corresponding of the straight line that the waveform of second half period of modulating wave is corresponding with V1 are designated as t respectively _5yAnd t _7y

t ₀-t ₁Time period, first switch transistor T 1 of control is turn-offed and conducting according to the sinusoid pulse width modulation modulation, and the second switch pipe T2 of control turn-offs, and the 8th switching tube TB2 in the control DC voltage booster circuit turn-offs;

t ₁-t _1yTime period, control said first switch transistor T 1 according to sinusoid pulse width modulation modulation conducting and shutoff, control said second switch pipe T2 conducting, control the 8th switching tube TB2 and turn-off;

t _1y-t _3yTime period, control the conducting of said second switch pipe, control said first switch transistor T 1, T2 according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube TB2 turn-offs and conducting according to the sinusoid pulse width modulation modulation;

t _3y-t ₃Time period, control said second switch pipe T2 according to sinusoid pulse width modulation modulation conducting and shutoff, control 1 conducting of said first switch transistor T, control the 8th switching tube TB2 and turn-off;

t ₅-t _5yTime period, control said first switch transistor T 1 according to sinusoid pulse width modulation modulation conducting and shutoff, control said second switch pipe T2 conducting, control the 8th switching tube TB2 and turn-off;

t _5y-t _7yTime period, control the conducting of said second switch pipe, control said first switch transistor T 1, T2 according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube TB2 turn-offs and conducting according to the sinusoid pulse width modulation modulation;

t _7y-t ₇Time period, control said second switch pipe T2 according to sinusoid pulse width modulation modulation conducting and shutoff, control 1 conducting of said first switch transistor T, control the 8th switching tube and turn-off;

t ₁-t _1yTime period, first kind of operation mode A and the 4th kind of operation mode D switch;

t _1y-t _3yTime period, first kind of operation mode A and the 5th kind of operation mode E switch;

t _3y-t ₃Time period, first kind of operation mode A and the third operation mode C switch;

t ₅-t _5yTime period, first kind of operation mode A and the 4th kind of operation mode D switch;

t _5y-t _7yTime period, first kind of operation mode A and the 5th kind of operation mode E switch;

t _7y-t ₇Time period, first kind of operation mode A and the third operation mode C switch;

Modulator approach based on seven level circuits in the said combining inverter of the invention described above embodiment; The present invention also provides the modulating device of seven level circuits in the said combining inverter of the embodiment of the invention, specifies its part below in conjunction with specific embodiment.

Referring to Fig. 7, this figure is the structure chart of the modulating device of seven level circuits in the said combining inverter of the embodiment of the invention.

Said modulating device is through the on off state of said first switch transistor T 1 of control, second switch pipe T2 and the 8th switching tube TB2, and the voltage that makes the common port of win capacitor C 1 and second capacitor C 2 is half of DC power supply output voltage V 1; The output voltage V 3 of said seven level circuits is the absolute value of line voltage;

Modulating device first embodiment of the described combining inverter of a kind of preamble embodiment specifically can comprise: first switch tube working status confirms that unit 11, the very first time confirm the unit 12 and first control unit 13.

First switch tube working status is confirmed unit 11; Be used for when DC power supply output voltage (when being applied to photovoltaic combining inverter; Being photovoltaic PV voltage or title MPPT maximum power point tracking voltage) when being higher than the peak value of modulating wave, said DC voltage booster circuit is not worked, and controls turning on and off of first and second switch transistor T 1, T2; Make said seven level circuits work according to five level adjustment modes, the 3rd to the 6th switch transistor T 3, T4, T5, T6 work according to power frequency commutation effect; Said modulating wave obtains after according to said line voltage sampling processing, and said modulating wave waveform is consistent with said grid voltage waveform;

The said very first time is confirmed unit 12, is used for confirming the time period of modulation; Be specially: modulating wave has three zero crossings in one-period T, be designated as t respectively ₀, t ₄And t ₈t ₄Mid point for cycle T; Obtain this three zero crossing t ₀, t ₄And t ₈With t ₀Postpone 1/4 mid point t that cycle T then was first half period ₂With t ₀Postpone 3/4 mid point t that cycle T then was second half period ₆The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1/2 respectively has two intersection points, and two intersection point time corresponding of the straight line that the waveform of note first half period of modulating wave is corresponding with V1/2 are respectively t ₁And t ₃, two intersection point time corresponding of the straight line that the waveform of note second half period of modulating wave is corresponding with V1/2 are respectively t ₅And t ₇The voltage of first electric capacity wherein, and the common port of second electric capacity is half V1/2 of direct voltage V1;

Said first control unit 13, first switching tube that is used to control and the on off state of second switch pipe are specially: t ₀-t ₁Time period, first switching tube of control turn-offs and conducting according to the sinusoid pulse width modulation modulation, and the second switch pipe of control turn-offs; t ₁-t ₂Time period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe; t ₂-t ₃Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting; t ₃-t ₄Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off; t ₄-t ₅Time period, control said first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said second switch pipe and turn-off; t ₅-t ₆Time period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe; t ₆-t ₇Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting; t ₇-t ₈Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off.

Need to prove that the very first time confirms that unit 12 obtains three the zero crossing ts of modulating wave at one-period T ₀, t ₄And t ₈A lot of middle implementations can be arranged, for example, can find out the moment of modulating wave zero crossing, obtain this three zero crossings through the phase-locked loop that is incorporated into the power networks.

Referring to Fig. 8, this figure is the structure chart of the modulating device of seven level circuits in the said combining inverter of the embodiment of the invention.

Said modulating device is through the on off state of control said first switching tube, second switch pipe and the 8th switching tube, and the voltage that makes the common port of the win electric capacity and second electric capacity is the half the of DC power supply output voltage V 1; Make the output voltage V 3 of said seven level circuits be the absolute value of line voltage.

Modulating device second embodiment of the said combining inverter of a kind of preamble embodiment specifically can comprise: the second switch plumber makes status determining unit 21, second time and confirms the unit 22 and second control unit 23;

The second switch plumber makes status determining unit 21; Be used for when DC power supply output voltage (when being applied to photovoltaic combining inverter; Be photovoltaic PV voltage or title MPPT maximum power point tracking voltage) when being higher than the peak value of modulating wave; Said DC voltage booster circuit work, first and second, eight switching tube T1, T2, TB2 work according to seven level adjustment modes;

Said second time is confirmed unit 22, is used for confirming the time period of modulation; Be specially: modulating wave has three zero crossings in one-period T, be designated as t respectively ₀, t ₄And t ₈t ₄Mid point for cycle T; Obtain this three zero crossing t ₀, t ₄And t ₈With t ₀Postpone 1/4 mid point t that cycle T then was first half period ₂With t ₀Postpone 3/4 mid point t that cycle T then was second half period ₆The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1/2 respectively has two intersection points, and two intersection point time corresponding of the straight line that the waveform of note first half period of modulating wave is corresponding with V1/2 are respectively t ₁And t ₃, two intersection point time corresponding of the straight line that the waveform of note second half period of modulating wave is corresponding with V1/2 are respectively t ₅And t ₇At time point t ₁And t ₂Between time point t is set _1x, at time point t ₂And t ₃Between time point t is set _3x, time point t _1xWith time point t _3xWith time point t ₂Be the center; At time point t ₅And t ₆Between time point t is set _5x, at time point t ₆And t ₇Between time point t is set _7x, time point t _5xWith time point t _7xWith time point t ₂Be the center; And t _1x-t _3xTime period equals t _5x-t _7xTime period; The voltage of first electric capacity wherein, and the common port of second electric capacity is half V1/2 of direct voltage V1; The voltage of the 4th capacitor C B1 is V2 in the said DC voltage booster circuit;

Said second control unit 23, the on off state of first switching tube that is used to control and second switch pipe and the 8th switching tube is specially: t ₀-t ₁Time period, first switching tube of control turn-offs and conducting according to the sinusoid pulse width modulation modulation, and control second switch pipe and the 8th switching tube turn-off; t ₁-t ₂Time period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe, control the 8th switching tube and turn-off; t _1x-t _3xTime period, control the conducting of said second switch pipe, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube turn-offs and conducting according to the sinusoid pulse width modulation modulation; t _3x-t ₃Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting, control the 8th switching tube and turn-off; t ₃-t ₄Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off, control the 8th switching tube and turn-off; t ₄-t ₅Time period, control said first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said second switch pipe and turn-off, control the 8th switching tube and turn-off; t ₅-t _5xTime period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe, control the 8th switching tube and turn-off; t _5x-t _7xTime period, control the conducting of said second switch pipe, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube turn-offs and conducting according to the sinusoid pulse width modulation modulation; t _7x-t ₇Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting, control the 8th switching tube and turn-off; t ₇-t ₈Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off, control the 8th switching tube and turn-off.

Need to prove that second time confirmed that unit 22 obtained three the zero crossing ts of modulating wave at one-period T ₀, t ₄And t ₈A lot of middle implementations can be arranged, for example, can find out the moment of modulating wave zero crossing, obtain this three zero crossings through the phase-locked loop that is incorporated into the power networks.

Referring to Fig. 9, this figure is the structure chart of modulating device the 3rd embodiment of seven level circuits in the said combining inverter of the embodiment of the invention.

Modulating device the 3rd embodiment of seven level circuits in the said combining inverter of the embodiment of the invention specifically can comprise: the 3rd switch tube working status confirms that unit 31, the 3rd time confirms unit 32 and the 3rd control unit 33.

The 3rd switch tube working status is confirmed the unit; Be used for when DC power supply output voltage (when being applied to photovoltaic combining inverter; Be photovoltaic PV voltage or title MPPT maximum power point tracking voltage) when being lower than the peak value of modulating wave; Said DC voltage booster circuit work, control first and second, the turning on and off of eight switching tube T1, T2, TB2, make said seven level circuits work according to seven level adjustment modes;

Said the 3rd time is confirmed the unit, is used for confirming the time period of modulation; Be specially: modulating wave has three zero crossings in one-period T, be designated as t respectively ₀, t ₄And t ₈t ₄Mid point for cycle T; Obtain this three zero crossing t ₀, t ₄And t ₈With t ₀Postpone 1/4 mid point t that cycle T then was first half period ₂With t ₀Postpone 3/4 mid point t that cycle T then was second half period ₆The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1/2 respectively has two intersection points, and two intersection point time corresponding of the straight line that the waveform of note first half period of modulating wave is corresponding with V1/2 are respectively t ₁And t ₃, two intersection point time corresponding of the straight line that the waveform of note second half period of modulating wave is corresponding with V1/2 are respectively t ₅And t ₇The straight line that the waveform of first half period of modulating wave and the waveform of second half period are corresponding with V1 respectively has two intersection points, and two intersection point time corresponding of the straight line that the waveform of first half period of modulating wave is corresponding with V1 are designated as t respectively _1yAnd t _3y, two intersection point time corresponding of the straight line that the waveform of second half period of modulating wave is corresponding with V1 are designated as t respectively _5yAnd t _7yThe voltage of first electric capacity wherein, and the common port of second electric capacity is half V1/2 of direct voltage V1; The voltage of the 4th capacitor C B1 is V2 in the said DC voltage booster circuit;

Said the 3rd control unit, the on off state of first switching tube that is used to control and second switch pipe and the 8th switching tube is specially: t ₀-t ₁Time period, first switching tube of control turn-offs and conducting according to the sinusoid pulse width modulation modulation, and control second switch pipe and the 8th switching tube turn-off; t ₁-t _1yTime period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe, control the 8th switching tube and turn-off; t _1y-t _2yTime period, control the conducting of said second switch pipe, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube turn-offs and conducting according to the sinusoid pulse width modulation modulation; t _2y-t ₃Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting, control the 8th switching tube and turn-off; t ₃-t ₄Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off, control the 8th switching tube and turn-off; t ₄-t ₅Time period, control said first switching tube and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said second switch pipe and turn-off, control the 8th switching tube and turn-off; t ₅-t _5yTime period, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff, control the conducting of said second switch pipe, control the 8th switching tube and turn-off; t _5y-t _7yTime period, control the conducting of said second switch pipe, control said first switching tube according to sinusoid pulse width modulation modulation conducting and shutoff; Controlling the 8th switching tube turn-offs and conducting according to the sinusoid pulse width modulation modulation; t _7y-t ₇Time period, control said second switch pipe according to sinusoid pulse width modulation modulation conducting and shutoff, control the said first switching tube conducting, control the 8th switching tube and turn-off; t ₇-t ₈Time period, control said second switch pipe and turn-off and conducting according to the sinusoid pulse width modulation modulation, control said first switching tube and turn-off, control the 8th switching tube and turn-off.

Need to prove that the 3rd time confirmed that unit 32 obtained three the zero crossing ts of modulating wave at one-period T ₀, t ₄And t ₈A lot of middle implementations can be arranged, for example, can find out the moment of modulating wave zero crossing, obtain this three zero crossings through the phase-locked loop that is incorporated into the power networks.

The invention also discloses a kind of combining inverter, comprise described seven level circuits of preamble, and the power frequency commutation inverter circuit parallelly connected with said seven level circuit outlet sides.

The invention also discloses a kind of combining inverter, comprise described seven level circuits of preamble, the power frequency commutation inverter circuit parallelly connected with said seven level circuit outlet sides, and between said seven level circuits and power frequency commutation inverter circuit, be parallel with the 3rd electric capacity.

The invention also discloses a kind of method of controlling combining inverter, said combining inverter comprises described seven level circuits of preamble, and said seven level circuits adopt the described any modulator approach of preamble.

The above only is preferred embodiment of the present invention, is not the present invention is done any pro forma restriction.Though the present invention discloses as above with preferred embodiment, yet be not in order to limit the present invention.Any those of ordinary skill in the art; Do not breaking away under the technical scheme scope situation of the present invention; All the method for above-mentioned announcement capable of using and technology contents are made many possible changes and modification to technical scheme of the present invention, or are revised as the equivalent embodiment of equivalent variations.Therefore, every content that does not break away from technical scheme of the present invention, all still belongs in the scope of technical scheme protection of the present invention any simple modification, equivalent variations and modification that above embodiment did according to technical spirit of the present invention.

Claims

1. a level circuit is characterized in that, the symmetric double Buck circuit that said seven level circuits comprise DC voltage booster circuit, are in parallel with DC power supply;

2. seven level circuits according to claim 1 is characterized in that, said DC chopper comprises: the 5th inductance and the 3rd diode of connecting between the positive bus-bar end of DC power supply and said the 4th capacitor C B1; The 7th switching tube that is provided with between the negative busbar end of the common port of the 5th inductance and the 3rd diode and DC power supply.

3. the modulator approach of seven level circuits according to claim 1 and 2 is characterized in that, comprising:

4. the modulator approach of described seven level circuits of claim 3 is characterized in that, comprising:

5. the modulator approach of seven level circuits according to claim 3 is characterized in that,

6. the modulator approach of seven level circuits according to claim 3 is characterized in that,

7. the modulating device of seven level circuits according to claim 1 and 2; It is characterized in that; Said modulating device is through the on off state of control said first switching tube, second switch pipe and the 8th switching tube, and the voltage that makes the common port of the win electric capacity and second electric capacity is the half the of DC power supply output voltage V 1; The output voltage V 3 of said seven level circuits is the absolute value of line voltage.

8. the modulating device of seven level circuits according to claim 7 is characterized in that, comprising: first switch tube working status confirms that unit, the very first time confirm the unit and first control unit;

9. the modulating device of seven level circuits according to claim 7 is characterized in that, said device comprises: the second switch plumber makes status determining unit, second time and confirms the unit and second control unit;

10. the modulating device of seven level circuits according to claim 7 is characterized in that, said device comprises: the 3rd switch tube working status confirms that unit, the 3rd time confirms unit and the 3rd control unit;

11. a combining inverter is characterized in that, comprises claim 1 or 2 described seven level circuits, and the power frequency commutation inverter circuit parallelly connected with said seven level circuit outlet sides.

12. combining inverter; It is characterized in that, comprise claim 1 or 2 described seven level circuits, the power frequency commutation inverter circuit parallelly connected with said seven level circuit outlet sides; And between said seven level circuits and power frequency commutation inverter circuit, be parallel with the 3rd electric capacity.

13. a method of controlling combining inverter is characterized in that, said combining inverter comprises claim 1 or 2 described seven level circuits, and said seven level circuits adopt like each described modulator approach of claim 3 to 6.

14. a device of controlling combining inverter is characterized in that, said combining inverter comprises claim 1 or 2 described seven level circuits, and said seven level circuits adopt like each described modulating device of claim 7 to 10.