Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of seven level and combining inverter and modulator approach and system, realizes the problem of taking into account leakage current and high efficiency two aspects.
The invention provides a kind of seven level circuits, the symmetric double Buck circuit that described seven level circuits comprise DC voltage booster circuit, are in parallel with DC power supply;
Described DC voltage booster circuit comprises: DC chopper and the 4th capacitor C B1 series connection, and the negative busbar end of DC power supply is connected with the 4th capacitor C B1, the positive bus-bar end connection DC chopper of DC power supply;
Between the common port of described DC chopper and the 4th capacitor C B1 and the first switching tube and the common port of the first diode, be connected with the 8th switching tube;
Described symmetric double Buck circuit comprises: after the first electric capacity and the second capacitances in series, be connected in parallel on described DC power supply both sides, in parallel with described DC power supply after the first diode and the series connection of the second diode, between the first electric capacity and the first diode, be provided with the first switching tube, between the second diode and the second electric capacity, be provided with second switch pipe; Between the common port of the first diode and the first switching tube and described seven level circuit outputs, be provided with the first inductance, between the common port of second switch pipe and the second diode and described seven level circuit outputs, be provided with the second inductance; The first electric capacity is directly connected with the tie point of the second diode with the first diode with the tie point of the second electric capacity.
Preferably, described DC chopper comprises: the 5th inductance and the 3rd diode of between the positive bus-bar end of DC power supply and described the 4th capacitor C B1, connecting; The 7th switching tube arranging between the common port of the 5th inductance and the 3rd diode and the negative busbar end of DC power supply.
Preferably, comprising:
Control the on off state of described the first switching tube, second switch pipe and the 8th switching tube, the voltage that makes the common port of the first electric capacity and the second electric capacity is half of DC power output voltage V1; The absolute value that the output voltage V 3 of described seven level circuits is line voltage;
Make the output voltage V 3 of described seven level circuits for take the sinuous pulsation of cycle T and continuous two positive half cycles, the waveform that peak value is line voltage peak value, described cycle T is the line voltage cycle.
The present invention also provides a kind of modulator approach of seven level circuits, comprising:
When DC power output voltage is during higher than the peak value of modulating wave, described DC voltage booster circuit is not worked, and controls turning on and off of first and second switching tube, and described seven level circuits are worked according to five level adjustment modes;
Described modulating wave has three zero crossings in one-period T, is designated as respectively t
0, t
4and t
8; t
4mid point for cycle T; Obtain this three zero crossing t
0, t
4and t
8;
By t
0postpone 1/4 mid point t that cycle T was the first half period
2; By t
0postpone 3/4 mid point t that cycle T was the second half period
6;
The waveform of the first half period of described modulating wave and the waveform of the second half period respectively straight line corresponding with V1/2 have two intersection points, are respectively t
1and t
3, and t
5and t
7;
T
0-t
1time period, control the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control second switch pipe and turn-off;
T
1-t
2time period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe;
T
2-t
3time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting;
T
3-t
4time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off;
T
4-t
5time period, control described the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described second switch pipe and turn-off;
T
5-t
6time period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe;
T
6-t
7time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting;
T
7-t
8time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off.
Preferably,
When DC power output voltage is during higher than the peak value of modulating wave, described DC voltage booster circuit work, control first and second, the turning on and off of eight switching tubes, described seven level circuits are worked according to seven level adjustment modes;
Modulating wave has three zero crossings in one-period T, is designated as respectively t
0, t
4and t
8; t
4mid point for cycle T; Obtain this three zero crossing t
0, t
4and t
8;
By t
0postpone 1/4 mid point t that cycle T was the first half period
2; By t
0postpone 3/4 mid point t that cycle T was the second half period
6;
The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1/2 have two intersection points, are designated as respectively t
1and t
3, and t
5and t
7;
At time point t
1and t
2between setup times point t
1x, at time point t
2and t
3between setup times point t
3x, time point t
1xwith time point t
3xwith time point t
2centered by;
At time point t
5and t
6between setup times point t
5x, at time point t
6and t
7between setup times point t
7x, time point t
5xwith time point t
7xwith time point t
2centered by; And t
1x-t
3xtime period equals t
5x-t
7xtime period;
T
0-t
1time period, control the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control second switch pipe and turn-off, control the 8th switching tube and turn-off;
T
1-t
1xtime period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe, control the 8th switching tube and turn-off;
T
1x-t
3xtime period, control the conducting of described second switch pipe, control the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation;
T
3x-t
3time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting, control the 8th switching tube and turn-off;
T
3-t
4time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off, control the 8th switching tube and turn-off;
T
4-t
5time period, control described the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described second switch pipe and turn-off, control the 8th switching tube and turn-off;
T
5-t
5xtime period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe, control the 8th switching tube and turn-off;
T
5x-t
7xtime period, control the conducting of described second switch pipe, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation;
T
7x-t
7time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting, control the 8th switching tube and turn-off;
T
7-t
8time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off, control the 8th switching tube and turn-off.
Preferably,
When DC power output voltage is during lower than the peak value of modulating wave, described DC voltage booster circuit work, control first and second, the turning on and off of eight switching tubes, described seven level circuits are worked according to seven level adjustment modes;
Modulating wave has three zero crossings in one-period T, is designated as respectively t
0, t
4and t
8; t
4mid point for cycle T; Obtain this three zero crossing t
0, t
4and t
8;
By t
0postpone 1/4 mid point t that cycle T was the first half period
2; By t
0postpone 3/4 mid point t that cycle T was the second half period
6;
The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1/2 have two intersection points, are designated as respectively t
1and t
3, and t
5and t
7;
The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1 have two intersection points, are designated as respectively t
1yand t
3y, and t
5yand t
7y;
T
0-t
1time period, control the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, to control second switch pipe and turn-off, the 8th switching tube of controlling in DC voltage booster circuit turn-offs;
T
1-t
1ytime period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe, control the 8th switching tube and turn-off;
T
1y-t
3ytime period, control the conducting of described second switch pipe, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation;
T
3y-t
3time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting, control the 8th switching tube and turn-off;
T
3-t
4time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off, control the 8th switching tube and turn-off;
T
4-t
5time period, control described the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described second switch pipe and turn-off, control the 8th switching tube and turn-off;
T
5-t
5ytime period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe, control the 8th switching tube and turn-off;
T
5y-t
7ytime period, control the conducting of described second switch pipe, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation;
T
7y-t
7time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting, control the 8th switching tube and turn-off;
T
7-t
8time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off, control the 8th switching tube and turn-off.
The present invention also provides a kind of modulating device of seven level circuits, described modulating device is by controlling the on off state of described the first switching tube, second switch pipe and the 8th switching tube, and the voltage that makes the common port of the first electric capacity and the second electric capacity is half of DC power output voltage V1; The absolute value that the output voltage V 3 of described seven level circuits is line voltage.
Preferably, comprising: the first switch tube working status determining unit, very first time determining unit and the first control unit;
Described the first switch tube working status determining unit, for when DC power output voltage is during higher than the amplitude of modulating wave, described DC voltage booster circuit is not worked, and controls turning on and off of first and second switching tube, and described seven level circuits are worked according to five level adjustment modes;
Described very first time determining unit, for determining the time period of modulation; Be specially: modulating wave has three zero crossings in one-period T, is designated as respectively t
0, t
4and t
8; t
4mid point for cycle T; Obtain this three zero crossing t
0, t
4and t
8; By t
0postpone 1/4 mid point t that cycle T was the first half period
2; By t
0postpone 3/4 mid point t that cycle T was the second half period
6; The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1/2 have two intersection points, are designated as respectively t
1and t
3, and t
5and t
7;
Described the first control unit, for controlling the on off state of the first switching tube and second switch pipe, is specially: t
0-t
1time period, control the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control second switch pipe and turn-off; t
1-t
2time period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe; t
2-t
3time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting; t
3-t
4time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off; t
4-t
5time period, control described the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described second switch pipe and turn-off; t
5-t
6time period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe; t
6-t
7time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting; t
7-t
8time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off.
Preferably, described device comprises: second switch pipe work status determining unit, the second time determining unit and the second control unit;
Described second switch pipe work status determining unit, for when DC power output voltage is during higher than the peak value of modulating wave, described DC voltage booster circuit work, control first and second, the turning on and off of eight switching tubes, described seven level circuits are worked according to seven level adjustment modes;
Described the second time determining unit, for determining the time period of modulation; Be specially: modulating wave has three zero crossings in one-period T, is designated as respectively t
0, t
4and t
8; t
4mid point for cycle T; Obtain this three zero crossing t
0, t
4and t
8; By t
0postpone 1/4 mid point t that cycle T was the first half period
2; By t
0postpone 3/4 mid point t that cycle T was the second half period
6; The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1/2 have two intersection points, are designated as respectively t
1and t
3, and t
5and t
7; At time point t
1and t
2between setup times point t
1x, at time point t
2and t
3between setup times point t
3x, time point t
1xwith time point t
3xwith time point t
2centered by; At time point t
5and t
6between setup times point t
5x, at time point t
6and t
7between setup times point t
7x, time point t
5xwith time point t
7xwith time point t
2centered by; And t
1x-t
3xtime period equals t
5x-t
7xtime period; In described DC voltage booster circuit, the voltage of the 4th capacitor C B1 is V2;
Described the second control unit, for controlling the on off state of the first switching tube and second switch pipe and the 8th switching tube, is specially: t
0-t
1time period, control the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control second switch pipe and the 8th switching tube and turn-off; t
1-t
2time period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe, control the 8th switching tube and turn-off; t
1x-t
3xtime period, control the conducting of described second switch pipe, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation; t
3x-t
3time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting, control the 8th switching tube and turn-off; t
3-t
4time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off, control the 8th switching tube and turn-off; t
4-t
5time period, control described the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described second switch pipe and turn-off, control the 8th switching tube and turn-off; t
5-t
5xtime period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe, control the 8th switching tube and turn-off; t
5x-t
7xtime period, control the conducting of described second switch pipe, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation; t
7x-t
7time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting, control the 8th switching tube and turn-off; t
7-t
8time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off, control the 8th switching tube and turn-off.
Preferably, described device comprises: the 3rd switch tube working status determining unit, the 3rd time determining unit and the 3rd control unit;
The 3rd switch tube working status determining unit, for when DC power output voltage is during lower than the peak value of modulating wave, described DC voltage booster circuit work, control first and second, the turning on and off of eight switching tubes, described seven level circuits are worked according to seven level adjustment modes;
Described the 3rd time determining unit, for determining the time period of modulation; Be specially: modulating wave has three zero crossings in one-period T, is designated as respectively t
0, t
4and t
8; t
4mid point for cycle T; Obtain this three zero crossing t
0, t
4and t
8; By t
0postpone 1/4 mid point t that cycle T was the first half period
2; By t
0postpone 3/4 mid point t that cycle T was the second half period
6; The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1/2 have two intersection points, are designated as respectively t
1and t
3, and t
5and t
7; The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1 have two intersection points, are designated as respectively t
1yand t
3y, and t
5yand t
7y; In described DC voltage booster circuit, the voltage of the 4th capacitor C B1 is V2;
Described the 3rd control unit, for controlling the on off state of the first switching tube and second switch pipe and the 8th switching tube, is specially: t
0-t
1time period, control the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control second switch pipe and the 8th switching tube and turn-off; t
1-t
2time period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe, control the 8th switching tube and turn-off; t
1y-t
3ytime period, control the conducting of described second switch pipe, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation; t
3y-t
3time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting, control the 8th switching tube and turn-off; t
3-t
4time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off, control the 8th switching tube and turn-off; t
4-t
5time period, control described the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described second switch pipe and turn-off, control the 8th switching tube and turn-off; t
5-t
5ytime period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe, control the 8th switching tube and turn-off; t
5y-t
7ytime period, control the conducting of described second switch pipe, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation; t
7y-t
7time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting, control the 8th switching tube and turn-off; t
7-t
8time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the 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 seven described level circuits, and the power frequency commutation inverter circuit in parallel with described seven level circuit outlet sides.
The present invention also provides a kind of combining inverter, comprises seven described level circuits, the power frequency commutation inverter circuit in parallel with described seven level circuit outlet sides, and between described 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 described combining inverter comprises seven described level circuits, and described seven level circuits adopt described modulator approach.
The present invention also provides a kind of device of controlling combining inverter, and described combining inverter comprises seven described level circuits, and described seven level circuits adopt described modulating device.
Compared with prior art, the present invention has the following advantages:
Seven level circuits described in the embodiment of the present invention, the symmetric double Buck circuit that comprises DC voltage booster circuit, is in parallel with DC power supply due to circuit; During described DC voltage booster circuit work, the seven level adjustment modes that can realize are worked.
When described in the embodiment of the present invention, seven level circuits are applied to combining inverter, can meet when prime DC power output voltage can not reach requiring of inverter voltage, by boosting of DC voltage booster circuit, thereby reach the requirement of inverter voltage, realize inversion.
The modulator approach of combining inverter and device described in the embodiment of the present invention, the first half period and the second half period at modulating wave are that the 3rd mode C and the 4th mode D appear in compartment of terrain, the voltage fluctuation producing in the first capacitor C 1 of two Buck circuit and the 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, greatly reduced the voltage undulation of first and second capacitor C 1, C2 and first and second inductance L 1, L2, thereby the ripple that reduces output voltage, has improved output waveform.And modulator approach and the device of combining inverter described in the embodiment of the present invention, can be so that switching tube, according to the regulative mode work of five level or seven level, have improved efficiency.Because number of levels increases, the voltage difference between level reduces simultaneously, and common-mode voltage is corresponding minimizing also, thereby has suppressed leakage current.
Embodiment
For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in detail.
Referring to Fig. 1, this is that the present invention's seven level circuits are applied to combining inverter the first embodiment circuit diagram.
Seven level circuits, the symmetric double Buck circuit that comprises DC voltage booster circuit, is in parallel with DC power supply.
Described DC voltage booster circuit comprises: DC chopper and the 4th capacitor C B1 series connection, and the negative busbar end of DC power supply is connected with the 4th capacitor C B1, the positive bus-bar end connection DC chopper of DC power supply;
Between the common port of described DC chopper and the 4th capacitor C B1 and the first switch transistor T 1 and the common port of the first diode D1, be connected with the 8th switching tube TB2.
Described symmetric double Buck circuit comprises: after the first capacitor C 1 and the second capacitor C 2 series connection, be connected in parallel on described DC power supply both sides, in parallel with described DC power supply after the first diode D1 and the second diode D2 series connection, between the first capacitor C 1 and the first diode D1, be provided with between the first switch transistor T 1, the second diode D2 and the second capacitor C 2 and be provided with second switch pipe T2; Between the common port of the first diode D1 and the first switch transistor T 1 and seven level circuit outputs, be provided with the first inductance L 1, between the common port of second switch pipe T2 and the second diode D2 and seven level circuit outputs, be provided with the second inductance L 2; The first electric capacity is directly connected with the tie point of the second diode with the first diode with the tie point of the second electric capacity.
Seven level circuits described in the embodiment of the present invention, the symmetric double Buck circuit that comprises DC voltage booster circuit, is in parallel with DC power supply due to circuit; During described DC voltage booster circuit work, the seven level adjustment modes that can realize are worked.
Referring to Fig. 1, when seven level circuits are applied to combining inverter described in the embodiment of the present invention, described inverter circuit comprises seven described level circuits, and the power frequency commutation inverter circuit being in parallel with described seven level circuits.
When described in first embodiment of the invention, seven level circuits are applied to combining inverter, can meet when DC power output voltage can not reach requiring of inverter voltage, by boosting of DC voltage booster circuit, thereby reach the requirement of inverter voltage, realize inversion.
Between described 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 combining inverter the second embodiment circuit diagram.
The difference of relative the first embodiment of second embodiment of the invention is, described DC chopper provides concrete implementation.
Described DC chopper comprises: the 5th inductance L B1 and the 3rd diode DB1 that between the positive bus-bar end of DC power supply and described the 4th capacitor C B1, connect; The 7th switching tube TB1 arranging 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 seven level circuits are applied to photovoltaic inverter circuit described in the embodiment of the present invention, described inverter circuit comprises seven described level circuits, and the power frequency commutation inverter circuit being in parallel with described seven level circuits.
When described in second embodiment of the invention, seven level circuits are applied to photovoltaic inverter circuit, prime photovoltaic cell output voltage can meet when can not reach requiring of inverter voltage, by boosting of DC voltage booster circuit, make the magnitude of voltage boosting of DC voltage booster circuit and the voltage sum of DC power supply reach the requirement of inverter voltage, thereby realize inversion.
Between described 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 seven level circuits described in the embodiment of the present invention, comprising:
Control the on off state of described the 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 first capacitor C 1 and the second capacitor C 2 is half of DC power output voltage V1; The output voltage V 3 that makes described seven level circuits is the absolute value of line voltage.
Referring to Fig. 3 a to Fig. 3 e, Fig. 3 a is the embodiment of the present invention seven level circuits the first operation mode A schematic diagrames of (also claiming two Buck circuit); Fig. 3 b is the embodiment of the present invention seven level circuits the second operation mode B schematic diagrames of (also claiming two Buck circuit); Fig. 3 c is the embodiment of the present invention seven level circuits the third operation mode C schematic diagrames of (also claiming two Buck circuit); Fig. 3 d is the embodiment of the present invention seven level circuits the 4th kind of operation mode D schematic diagrames of (also claiming two Buck circuit); Fig. 3 e is the 5th kind of operation mode E schematic diagram of the embodiment of the present invention seven level circuits.
The first 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 load supplying simultaneously, and now the 3rd capacitor C 3 voltages are DC power supply voltage V1, i.e. V3=V1.
The second 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 by 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: the first switch transistor T 1 conducting, second, eight switching tube T2, TB2 turn-off.The first capacitor C 1 is load supplying, 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.The second capacitor C 2 is load supplying, 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: the first switch transistor T 1 is turn-offed, second, eight switching tube T2, TB2 conducting simultaneously.The 4th capacitor C B1 is load supplying, and the voltage of the 3rd capacitor C 3 is V2, i.e. V3=V2.
Referring to Fig. 4, it is the schematic diagram of modulator approach first embodiment of seven level circuits in combining inverter described in the embodiment of the present invention.
In Fig. 4, the instantaneous value of grid-connected absolute value of voltage is u, and the instantaneous value of grid-connected current is i.Because modulating wave is according to obtaining after described line voltage sampling processing, described modulating wave waveform and described grid voltage waveform are basically identical, and difference can be ignored.Therefore in figure, adopt grid voltage waveform, can be considered to modulating wave.
The modulator approach of seven level circuits that the present embodiment provides, the voltage of the common port of the first capacitor C 1 and the second capacitor C 2 is that half of direct voltage V1 is V1/2;
When DC power output voltage is during higher than the peak value of modulating wave, described DC voltage booster circuit is 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, when judgement photovoltaic PV voltage also claims the peak value of MPPT maximum power point tracking voltage (MPPT) higher than modulating wave, described 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.
Grid-connected voltage has three zero crossings in one-period T, is designated as respectively t0, t4 and t8; T4 is the mid point of cycle T; Obtain this three zero crossing t
0, t
4and t
8.
By t
0postpone 1/4 mid point t that cycle T was the first half period
2; By t
0postpone 3/4 mid point t that cycle T was the second half period
6.
The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1/2 have two intersection points, and two times corresponding to intersection point of the straight line that the waveform of note the first half period of modulating wave is corresponding with V1/2 are respectively t
1and t
3, two times corresponding to intersection point of the waveform straight line corresponding with V1/2 of note the second half period of modulating wave are respectively t
5and t
7.
T
0-t
1time period, control the first switch transistor T 1 and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control second switch pipe T2 and turn-off;
T
1-t
2time period, control described the first switch transistor T 1 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described second switch pipe T2 conducting;
T
2-t
3time period, control described second switch pipe T2 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switch transistor T 1 conducting;
T
3-t
4time period, control described second switch pipe T2 and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switch transistor T 1 and turn-off;
T
4-t
5time period, control described the first switch transistor T 1 and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described second switch pipe T2 and turn-off;
T
5-t
6time period, control described the first switch transistor T 1 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described second switch pipe T2 conducting;
T
6-t
7time period, control described second switch pipe T2 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switch transistor T 1 conducting;
T
7-t
8time period, control described second switch pipe T2 and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switch transistor T 1 and turn-off.
It should be noted that, switching tube turn-on and turn-off discontinuously in the embodiment of the present invention, to be realized by drive pulse signal, for example, drive pulse signal is provided to the control end of the first switch transistor T 1, the first switch transistor T 1 conducting in the high level time section of drive pulse signal, 1 shutoff of the first switch transistor T in the low level time section of drive pulse signal.The turn-on and turn-off condition of second switch pipe T2 is similar.This drive pulse signal obtains according to Using Sinusoidal Pulse Width Modulation.
As seen from Figure 4, t
0-t
1time period, the third operation mode C of the second operation mode B of the present invention's seven level circuits and the present invention's seven level circuits switches;
T
1-t
2time period, the 4th kind of operation mode D of the first 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, the third operation mode C of the first operation mode A of the present invention's seven level circuits and the present invention's seven level circuits switches;
T
3-t
4time period, the 4th kind of operation mode D of the second 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, the third operation mode C of the second operation mode B of the present invention's seven level circuits and the present invention's seven level circuits switches;
T
5-t
6time period, the 4th kind of operation mode D of the first 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, the third operation mode C of the first operation mode A of the present invention's seven level circuits and the present invention's seven level circuits switches;
T
7-t
8time period, the 4th kind of operation mode D of the second operation mode B of the present invention's seven level circuits and the present invention's seven level circuits switches.
As can be seen from Figure 4, the operation mode switching in the first half period of modulating wave is respectively BC, AD, AC and BD.Because circuit structure in the first operation mode A and the second operation mode B is symmetrical, in the first operation mode A, the state of the first capacitor C 1, the second capacitor C 2 is identical, electric discharge simultaneously, therefore, during the first operation mode A, can think that the voltage of DC power supply is constant, the mid point electric current of the first capacitor C 1 and the second capacitor C 2 is zero, and it is constant that the voltage of the first capacitor C 1 and the second capacitor C 2 keeps, and can not be offset.
In the second operation mode B, the state of the first capacitor C 1 and the second capacitor C 2 is also identical, do not discharge simultaneously, therefore, during the second operation mode B, can think that the mid point electric current of the first capacitor C 1 and the second capacitor C 2 is zero, it is constant that the voltage of the first capacitor C 1 and the second capacitor C 2 keeps, and can not be offset.Therefore, in the first capacitor C 1 and the second capacitor C 2, voltage stabilization can not produce fluctuation.Therefore, in modulation, the voltage fluctuation in the time of can not considering the first operation mode A and the second operation mode B in the first capacitor C 1 and the second capacitor C 2.
During the third operation mode C, the first capacitor C 1 electric discharge, the second capacitor C 2 chargings.The voltage of such the first capacitor C 1 and the second capacitor C 2 is offset.
During the 4th kind of operation mode D, the first capacitor C 1 charging, the second capacitor C 2 electric discharges.Like this, the voltage of the first capacitor C 1 and the second capacitor C 2 is offset.
Voltage fluctuation when therefore, the embodiment of the present invention is mainly considered the third operation mode C and the 4th kind of operation mode D in the first capacitor C 1 and the second capacitor C 2.In the 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 effectively offset the voltage fluctuation producing in the first capacitor C 1 and the second capacitor C 2 in the third operation mode C and the 4th kind of operation mode D.In like manner, the operation mode switching in the second half period of modulating wave is also 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 the first half period of modulating wave, t
0-t
1time period the third operation mode C makes the first capacitor C 1 electric discharge, voltage drop; t
1-t
2time period the 4th kind of operation mode D makes the first capacitor C 1 charging, and voltage rises; t
2-t
3time period, the third operation mode C makes the first capacitor C 1 electric discharge, voltage drop; The t3-t4 time period, the 4th kind of operation mode D makes the first capacitor C 1 charging, and voltage rises.
The modulator approach of seven level circuits provided by the invention, the voltage fluctuation in the first capacitor C 1 reduces significantly.Similar due in the fluctuation voltage in the second capacitor C 2 and the first capacitor C 1, does not repeat them here.
The modulator approach of seven level circuits that the embodiment of the present invention provides, the first half period and the second half period at modulating wave are that the third operation mode C and the 4th kind of operation mode D appear in compartment of terrain, the voltage fluctuation producing in the first capacitor C 1 and the second capacitor C 2 in the time of can effectively offsetting like this third operation mode C and the 4th kind of operation mode D.And continuous discharge and the lasting charging interval of the first capacitor C 1, the second capacitor C 2 and the first inductance L 1, the second inductance L 2 are all shorter, greatly reduced the voltage undulation of the first capacitor C 1, the second capacitor C 2 and the first inductance L 1, the second inductance L 2, thereby the ripple that reduces output voltage, has improved output waveform.
It should be noted that, obtain modulating wave at three zero crossing t of one-period T
0, t
4and t
8can there be a lot of implementations, for example, can by grid-connected phase-locked loop, find out the moment of modulating wave zero crossing, obtain this three zero crossings.
It should be noted that, described cycle T determines by mains frequency, and for example, when mains frequency is 50Hz, described cycle T is 20ms.
Referring to Fig. 5, this figure is the schematic diagram of modulator approach second embodiment of seven level circuits in combining inverter described in the embodiment of the present invention.
When DC power output voltage is (while being applied to photovoltaic combining inverter, for photovoltaic PV voltage or MPPT maximum power point tracking voltage) during higher than the peak value of modulating wave, described DC voltage booster circuit work, first and second, eight switching tube T1, T2, TB2 can work according to seven level adjustment modes.
In this case, DC power output voltage V1 has reached the peak value of line voltage to Fig. 5, but now direct current boost booster circuit works on, and makes the output voltage V 2 of DC voltage booster circuit be greater than DC power output voltage V1.
Wherein: when making to adopt the modulator approach shown in Fig. 5, the efficiency of seven level circuits is higher than the efficiency that adopts modulator approach shown in Fig. 4.
To t
1x, t
3x(t
1x-t
3xbe DC voltage booster circuit working hour) provided two design criterions and be limited.
(1) in the situation that meeting THD requirement, as long as meet DC voltage booster circuit output voltage V
2be greater than DC power 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 having increased a level modulation, all in all, still can guarantee that the efficiency of seven level circuits is higher.
(2) in the situation that meeting THD requirement, t
1xvalue is more a little bit smaller as much as possible, to guarantee from 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 still can guarantee that the efficiency of seven level circuits is higher.
In sum, while adopting the modulator approach shown in Fig. 5, can realize seven level, so efficiency is higher than the efficiency that adopts modulator approach shown in Fig. 4.
The voltage of the first electric capacity in the present invention's seven level circuits and the common port of the second electric capacity is that half of direct voltage V1 is V1/2; In described DC voltage booster circuit, the voltage of the 4th capacitor C B1 is V2;
Modulating wave has three zero crossings in one-period T, is designated as respectively t
0, t
4and t
8; t
4mid point for cycle T; Obtain this three zero crossing t
0, t
4and t
8;
By t
0postpone 1/4 mid point t that cycle T was the first half period
2; By t
0postpone 3/4 mid point t that cycle T was the second half period
6;
The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1/2 have two intersection points, and the time corresponding to two intersection points of the straight line that the waveform of the first half period of modulating wave is corresponding with V1/2 is designated as respectively t
1and t
3, the time corresponding to two intersection points of the straight line that the waveform of the second half period of modulating wave is corresponding with V1/2 is designated as respectively t
5and t
7;
At time point t
1and t
2between setup times point t
1x, at time point t
2and t
3between setup times point t
2x, time point t
1xwith time point t
2xwith time point t
2centered by;
At time point t
5and t
6between setup times point t
5x, at time point t
6and t
7between setup times point t
7x, time point t
5xwith time point t
7xwith time point t
2centered by; And t
1x-t
2xtime period equals t
5x-t
7xtime period;
T
0-t
1time period, control the first switch transistor T 1 and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control second switch pipe T2 and turn-off, the 8th switching tube TB2 controlling in DC voltage booster circuit turn-offs;
T
1-t
1xtime period, control described the first switch transistor T 1 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described second switch pipe T2 conducting, control the 8th switching tube TB2 and turn-off;
T
1x-t
2xtime period, control the conducting of described second switch pipe, control described the first switch transistor T 1, T2 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube TB2 turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation;
T
2x-t
3time period, control described second switch pipe T2 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switch transistor T 1 conducting, control the 8th switching tube TB2 and turn-off;
T
3-t
4time period, control described second switch pipe T2 and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switch transistor T 1 and turn-off, control the 8th switching tube TB2 and turn-off;
T
4-t
5time period, control described the first switch transistor T 1 and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described second switch pipe T2 and turn-off, control the 8th switching tube TB2 and turn-off;
T
5-t
5xtime period, control described the first switch transistor T 1 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described second switch pipe T2 conducting, control the 8th switching tube TB2 and turn-off;
T
5x-t
7xtime period, control the conducting of described second switch pipe, control described the first switch transistor T 1, T2 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube TB2 turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation;
T
7x-t
7time period, control described second switch pipe T2 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switch transistor T 1 conducting, control the 8th switching tube TB2 and turn-off;
T
7-t
8time period, control described second switch pipe T2 and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switch transistor T 1 and turn-off, control the 8th switching tube TB2 and turn-off.
As seen from Figure 5, t
0-t
1time period, the second operation mode B and the third operation mode C switch;
T
1-t
1xtime period, the first operation mode A and the 4th kind of operation mode D switch;
T
1x-t
2xtime period, the first operation mode A and the 5th kind of operation mode E switch;
T
2x-t
3time period, the first operation mode A and the third operation mode C switch;
T
3-t
4time period, the second operation mode B and the 4th kind of operation mode D switch;
T
4-t
5time period, the second operation mode B and the third operation mode C switch;
T
5-t
5xtime period, the first operation mode A and the 4th kind of operation mode D switch;
T
5x-t
7xtime period, the first operation mode A and the 5th kind of operation mode E switch;
T
7x-t
7time period, the first operation mode A and the third operation mode C switch;
T
7-t
8time period, the second 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 combining inverter of the present invention.
When DC power output voltage is (when being applied to photovoltaic combining inverter, for photovoltaic PV voltage or MPPT maximum power point tracking voltage) during lower than the peak value of modulating wave, described DC voltage booster circuit work, control first and second, the turning on and off of eight switching tube T1, T2, TB2, described seven level circuits are worked according to seven level adjustment modes;
The voltage of the first capacitor C 1 in the present invention's seven level circuits and the common port of the second capacitor C 2 is that half of direct voltage V1 is V1/2; In described DC voltage booster circuit, the voltage of the 4th capacitor C B1 is V2;
Modulating wave has three zero crossings in one-period T, is designated as respectively t
0, t
4and t
8; t
4mid point for cycle T; Obtain this three zero crossing t
0, t
4and t
8;
By t
0postpone 1/4 mid point t that cycle T was the first half period
2; By t
0postpone 3/4 mid point t that cycle T was the second half period
6;
The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1/2 have two intersection points, and the time corresponding to two intersection points of the straight line that the waveform of the first half period of modulating wave is corresponding with V1/2 is designated as respectively t
1and t
3, the time corresponding to two intersection points of the straight line that the waveform of the second half period of modulating wave is corresponding with V1/2 is designated as respectively t
5and t
7;
The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1 have two intersection points, and the time corresponding to two intersection points of the straight line that the waveform of the first half period of modulating wave is corresponding with V1 is designated as respectively t
1yand t
3y, the time corresponding to two intersection points of the straight line that the waveform of the second half period of modulating wave is corresponding with V1 is designated as respectively t
5yand t
7y;
T
0-t
1time period, the first switch transistor T 1 of control is turn-offed and conducting according to Using Sinusoidal Pulse Width Modulation, and the second switch pipe T2 of control turn-offs, and the 8th switching tube TB2 controlling in DC voltage booster circuit turn-offs;
T
1-t
1ytime period, control described the first switch transistor T 1 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described second switch pipe T2 conducting, control the 8th switching tube TB2 and turn-off;
T
1y-t
3ytime period, control the conducting of described second switch pipe, control described the first switch transistor T 1, T2 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube TB2 turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation;
T
3y-t
3time period, control described second switch pipe T2 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switch transistor T 1 conducting, control the 8th switching tube TB2 and turn-off;
T
3-t
4time period, control described second switch pipe T2 and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switch transistor T 1 and turn-off, control the 8th switching tube TB2 and turn-off;
T
4-t
5time period, control described the first switch transistor T 1 and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described second switch pipe T2 and turn-off, control the 8th switching tube TB2 and turn-off;
T
5-t
5ytime period, control described the first switch transistor T 1 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described second switch pipe T2 conducting, control the 8th switching tube TB2 and turn-off;
T
5y-t
7ytime period, control the conducting of described second switch pipe, control described the first switch transistor T 1, T2 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube TB2 turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation;
T
7y-t
7time period, control described second switch pipe T2 according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switch transistor T 1 conducting, control the 8th switching tube and turn-off;
T
7-t
8time period, control described second switch pipe T2 and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switch transistor T 1 and turn-off, control the 8th switching tube TB2 and turn-off.
As seen from Figure 5, t
0-t
1time period, the second operation mode B and the third operation mode C switch;
T
1-t
1ytime period, the first operation mode A and the 4th kind of operation mode D switch;
T
1y-t
3ytime period, the first operation mode A and the 5th kind of operation mode E switch;
T
3y-t
3time period, the first operation mode A and the third operation mode C switch;
T
3-t
4time period, the second operation mode B and the 4th kind of operation mode D switch;
T
4-t
5time period, the second operation mode B and the third operation mode C switch;
T
5-t
5ytime period, the first operation mode A and the 4th kind of operation mode D switch;
T
5y-t
7ytime period, the first operation mode A and the 5th kind of operation mode E switch;
T
7y-t
7time period, the first operation mode A and the third operation mode C switch;
T
7-t
8time period, the second operation mode B and the 4th kind of operation mode D switch.
Modulator approach based on seven level circuits in combining inverter described in the invention described above embodiment, the present invention also provides described in the embodiment of the present invention modulating device of seven level circuits in combining inverter, below in conjunction with specific embodiment, describes its part in detail.
Referring to Fig. 7, this figure is the structure chart of the modulating device of seven level circuits in combining inverter described in the embodiment of the present invention.
Described modulating device is by controlling the on off state of described the first switch transistor T 1, second switch pipe T2 and the 8th switching tube TB2, and the voltage that makes the common port of the first capacitor C 1 and the second capacitor C 2 is half of DC power output voltage V1; The absolute value that the output voltage V 3 of described seven level circuits is line voltage;
Modulating device first embodiment for combining inverter described in embodiment, specifically can comprise: the first switch tube working status determining unit 11, very first time determining unit 12 and the first control unit 13 above.
The first switch tube working status determining unit 11, be used for when DC power output voltage is (while being applied to photovoltaic combining inverter, for photovoltaic PV voltage or claim MPPT maximum power point tracking voltage) during higher than the peak value of modulating wave, described DC voltage booster circuit is not worked, control turning on and off of first and second switch transistor T 1, T2, described seven level circuits are worked according to five level adjustment modes, and the 3rd to the 6th switch transistor T 3, T4, T5, T6 work according to power frequency commutation effect; Described modulating wave is according to obtaining after described line voltage sampling processing, and described modulating wave waveform is consistent with described grid voltage waveform;
Described very first time determining unit 12, for determining the time period of modulation; Be specially: modulating wave has three zero crossings in one-period T, is designated as respectively t
0, t
4and t
8; t
4mid point for cycle T; Obtain this three zero crossing t
0, t
4and t
8; By t
0postpone 1/4 mid point t that cycle T was the first half period
2; By t
0postpone 3/4 mid point t that cycle T was the second half period
6; The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1/2 have two intersection points, and two times corresponding to intersection point of the straight line that the waveform of note the first half period of modulating wave is corresponding with V1/2 are respectively t
1and t
3, two times corresponding to intersection point of the waveform straight line corresponding with V1/2 of note the second half period of modulating wave are respectively t
5and t
7; The voltage of the first electric capacity wherein, and the common port of the second electric capacity is half V1/2 of direct voltage V1;
Described the first control unit 13, for the first switching tube of controlling and the on off state of second switch pipe, is specially: t
0-t
1time period, the first switching tube of control turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation, and the second switch pipe of control turn-offs; t
1-t
2time period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe; t
2-t
3time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting; t
3-t
4time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off; t
4-t
5time period, control described the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described second switch pipe and turn-off; t
5-t
6time period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe; t
6-t
7time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting; t
7-t
8time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off.
It should be noted that, very first time determining unit 12 obtains modulating wave at three zero crossing t of one-period T
0, t
4and t
8can there be a lot of middle implementations, for example, can by grid-connected phase-locked loop, find out the moment of modulating wave zero crossing, obtain this three zero crossings.
It should be noted that, described cycle T determines by mains frequency, and for example, when mains frequency is 50Hz, described cycle T is 20ms.
Referring to Fig. 8, this figure is the structure chart of the modulating device of seven level circuits in combining inverter described in the embodiment of the present invention.
Described modulating device is by controlling the on off state of described the first switching tube, second switch pipe and the 8th switching tube, and the voltage that makes the common port of the first electric capacity and the second electric capacity is half of DC power output voltage V1; The output voltage V 3 that makes described seven level circuits is the absolute value of line voltage.
Modulating device second embodiment for combining inverter described in embodiment, specifically can comprise: second switch pipe work status determining unit 21, the second time determining unit 22 and the second control unit 23 above;
Second switch pipe work status determining unit 21, be used for when DC power output voltage is (while being applied to photovoltaic combining inverter, for photovoltaic PV voltage or claim MPPT maximum power point tracking voltage) during higher than the peak value of modulating wave, described DC voltage booster circuit work, first and second, eight switching tube T1, T2, TB2 work according to seven level adjustment modes;
Described the second time determining unit 22, for determining the time period of modulation; Be specially: modulating wave has three zero crossings in one-period T, is designated as respectively t
0, t
4and t
8; t
4mid point for cycle T; Obtain this three zero crossing t
0, t
4and t
8; By t
0postpone 1/4 mid point t that cycle T was the first half period
2; By t
0postpone 3/4 mid point t that cycle T was the second half period
6; The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1/2 have two intersection points, and two times corresponding to intersection point of the straight line that the waveform of note the first half period of modulating wave is corresponding with V1/2 are respectively t
1and t
3, two times corresponding to intersection point of the waveform straight line corresponding with V1/2 of note the second half period of modulating wave are respectively t
5and t
7; At time point t
1and t
2between setup times point t
1x, at time point t
2and t
3between setup times point t
3x, time point t
1xwith time point t
3xwith time point t
2centered by; At time point t
5and t
6between setup times point t
5x, at time point t
6and t
7between setup times point t
7x, time point t
5xwith time point t
7xwith time point t
2centered by; And t
1x-t
3xtime period equals t
5x-t
7xtime period; The voltage of the first electric capacity wherein, and the common port of the second electric capacity is half V1/2 of direct voltage V1; In described DC voltage booster circuit, the voltage of the 4th capacitor C B1 is V2;
Described the second control unit 23, for the first switching tube of controlling and the on off state of second switch pipe and the 8th switching tube, is specially: t
0-t
1time period, the first switching tube of control turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation, controls second switch pipe and the 8th switching tube and turn-offs; t
1-t
2time period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe, control the 8th switching tube and turn-off; t
1x-t
3xtime period, control the conducting of described second switch pipe, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation; t
3x-t
3time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting, control the 8th switching tube and turn-off; t
3-t
4time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off, control the 8th switching tube and turn-off; t
4-t
5time period, control described the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described second switch pipe and turn-off, control the 8th switching tube and turn-off; t
5-t
5xtime period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe, control the 8th switching tube and turn-off; t
5x-t
7xtime period, control the conducting of described second switch pipe, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation; t
7x-t
7time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting, control the 8th switching tube and turn-off; t
7-t
8time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off, control the 8th switching tube and turn-off.
It should be noted that, the second time determining unit 22 obtains modulating wave at three zero crossing t of one-period T
0, t
4and t
8can there be a lot of middle implementations, for example, can by grid-connected phase-locked loop, find out the moment of modulating wave zero crossing, obtain this three zero crossings.
It should be noted that, described cycle T determines by mains frequency, and for example, when mains frequency is 50Hz, described cycle T is 20ms.
Referring to Fig. 9, this figure is the structure chart of modulating device the 3rd embodiment of seven level circuits in combining inverter described in the embodiment of the present invention.
The modulating device of seven level circuits the 3rd embodiment in combining inverter described in the embodiment of the present invention, specifically can comprise: the 3rd switch tube working status determining unit 31, the 3rd time determining unit 32 and the 3rd control unit 33.
The 3rd switch tube working status determining unit, be used for when DC power output voltage is (while being applied to photovoltaic combining inverter, for photovoltaic PV voltage or claim MPPT maximum power point tracking voltage) during lower than the peak value of modulating wave, described DC voltage booster circuit work, control first and second, the turning on and off of eight switching tube T1, T2, TB2, described seven level circuits are worked according to seven level adjustment modes;
Described the 3rd time determining unit, for determining the time period of modulation; Be specially: modulating wave has three zero crossings in one-period T, is designated as respectively t
0, t
4and t
8; t
4mid point for cycle T; Obtain this three zero crossing t
0, t
4and t
8; By t
0postpone 1/4 mid point t that cycle T was the first half period
2; By t
0postpone 3/4 mid point t that cycle T was the second half period
6; The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1/2 have two intersection points, and two times corresponding to intersection point of the straight line that the waveform of note the first half period of modulating wave is corresponding with V1/2 are respectively t
1and t
3, two times corresponding to intersection point of the waveform straight line corresponding with V1/2 of note the second half period of modulating wave are respectively t
5and t
7; The waveform of the first half period of modulating wave and the waveform of the second half period respectively straight line corresponding with V1 have two intersection points, and the time corresponding to two intersection points of the straight line that the waveform of the first half period of modulating wave is corresponding with V1 is designated as respectively t
1yand t
3y, the time corresponding to two intersection points of the straight line that the waveform of the second half period of modulating wave is corresponding with V1 is designated as respectively t
5yand t
7y; The voltage of the first electric capacity wherein, and the common port of the second electric capacity is half V1/2 of direct voltage V1; In described DC voltage booster circuit, the voltage of the 4th capacitor C B1 is V2;
Described the 3rd control unit, for the first switching tube of controlling and the on off state of second switch pipe and the 8th switching tube, is specially: t
0-t
1time period, the first switching tube of control turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation, controls second switch pipe and the 8th switching tube and turn-offs; t
1-t
1ytime period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe, control the 8th switching tube and turn-off; t
1y-t
2ytime period, control the conducting of described second switch pipe, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation; t
2y-t
3time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting, control the 8th switching tube and turn-off; t
3-t
4time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off, control the 8th switching tube and turn-off; t
4-t
5time period, control described the first switching tube and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described second switch pipe and turn-off, control the 8th switching tube and turn-off; t
5-t
5ytime period, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control the conducting of described second switch pipe, control the 8th switching tube and turn-off; t
5y-t
7ytime period, control the conducting of described second switch pipe, control described the first switching tube according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off; Controlling the 8th switching tube turn-offs and conducting according to Using Sinusoidal Pulse Width Modulation; t
7y-t
7time period, control described second switch pipe according to Using Sinusoidal Pulse Width Modulation turn-on and turn-off, control described the first switching tube conducting, control the 8th switching tube and turn-off; t
7-t
8time period, control described second switch pipe and turn-off and conducting according to Using Sinusoidal Pulse Width Modulation, control described the first switching tube and turn-off, control the 8th switching tube and turn-off.
It should be noted that, the 3rd time determining unit 32 obtains modulating wave at three zero crossing t of one-period T
0, t
4and t
8can there be a lot of middle implementations, for example, can by grid-connected phase-locked loop, find out the moment of modulating wave zero crossing, obtain this three zero crossings.
It should be noted that, described cycle T determines by mains frequency, and for example, when mains frequency is 50Hz, described cycle T is 20ms.
The invention also discloses a kind of combining inverter, comprise previously described seven level circuits, and the power frequency commutation inverter circuit in parallel with described seven level circuit outlet sides.
The invention also discloses a kind of combining inverter, comprise previously described seven level circuits, the power frequency commutation inverter circuit in parallel with described seven level circuit outlet sides, and between described 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, described combining inverter comprises previously described seven level circuits, and described seven level circuits adopt previously described any modulator approach.
The above, be only preferred embodiment of the present invention, not the present invention done to any pro forma restriction.Although the present invention discloses as above with preferred embodiment, yet not in order to limit the present invention.Any those of ordinary skill in the art, do not departing from technical solution of the present invention scope situation, all can utilize method and the technology contents of above-mentioned announcement to make many possible changes and modification to technical solution of the present invention, or be revised as the equivalent embodiment of equivalent variations.Therefore, every content that does not depart from technical solution of the present invention,, all still belongs in the scope of technical solution of the present invention protection any simple modification made for any of the above embodiments, equivalent variations and modification according to technical spirit of the present invention.