CN104022669A - Neutral point clamp photovoltaic inverter and modulation method thereof - Google Patents
Neutral point clamp photovoltaic inverter and modulation method thereof Download PDFInfo
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- CN104022669A CN104022669A CN201410294366.4A CN201410294366A CN104022669A CN 104022669 A CN104022669 A CN 104022669A CN 201410294366 A CN201410294366 A CN 201410294366A CN 104022669 A CN104022669 A CN 104022669A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention discloses a neutral point clamp photovoltaic inverter and a modulation method thereof. The modulation method comprises the following steps: acquiring a reference voltage vector required for modulation; establishing a basic space vector distribution diagram of the photovoltaic inverter, wherein the basic space vector comprises a zero vector, six long vectors, six middle vectors and six short vectors; selecting three adjacent middle vectors to synthesize the reference voltage vector according to the region of the reference voltage vector under an alpha beta coordiate system; selecting two adjacent middle vectors and one zero vector to synthesize the reference voltage vector according to the region of the reference voltage vector under the alpha beta coordinate system; and determining the basic space vector of the synthesized reference voltage vector by combining with constraint conditions as few as possible of power switch pipes changing in state at the same time. According to the invention, the system common-mode voltage is always stabilized at a certain constant value, and the generation of system high-frequency common mode leakage current is reduced effectively.
Description
Technical field
The invention belongs to electric and electronic technical field, be specially a kind of neutral point clamper photovoltaic DC-to-AC converter and modulator approach thereof.
Background technology
Solar energy power generating can replace resource-constrained, non-renewable fossil energy such as coal, oil and natural gas and the secondary energy sources that converted to by primary energy, therefore promote solar energy power generating application, to reducing consumption figure and the Optimization of Energy Structure of fossil energy, significant.
Wherein, non-isolation type combining inverter is owing to having reduced the power loss of transformer stage, and has that efficiency is high, volume is little, cost is low and the feature such as simple in structure, in recent years, worldwide obtained development fast.But owing to having lacked transformer, between photovoltaic cell and electrical network, there is electrical connection, brought potential safety hazard simultaneously; In addition, all there is parasitic capacitance over the ground in photovoltaic cell and inverter grounding shell, and form resonant tank with output filtering element and electric network impedance that inverter has, and then inverter carries out HF switch when action, can cause the variation of voltage on aforementioned parasitic electric capacity, easily cause in loop common mode current to exceed allowed band and occur leaky.The existence of common mode leakage current has reduced generating efficiency and the grid-connected quality of system on the one hand over the ground, can bring on the other hand serious electromagnetic compatibility problem, causes a hidden trouble to equipment and personnel's safety.
Simultaneously, along with the continuous increase of photovoltaic installed capacity, as the core devices of new energy resources system energy conversion, the capacity of inverter and the requirement of voltage withstand class are also more and more higher, traditional two-level inverter cannot meet the demands, therefore multilevel converter progressively becomes the focus of research.Multi-electrical level inverter has advantages of that voltage withstand class is high, voltage stress is low and the aberration rate of voltage and current is low, but along with increasing of level number, the complexity of control strategy sharply increases, and for these reasons, three-level inverter demonstrates great superiority.
The main topological structure of traditional three-phase photovoltaic DC-to-AC converter based on neutral point clamper generally adopts SVPWM modulation system, it has the advantages such as direct voltage utilance is high, output current harmonics content is low, but this kind of topological structure and modulation system can cause the photovoltaic cell high-frequency fluctuation of parasitic capacitance both end voltage over the ground, thereby inevitably produce common mode leakage current.
Summary of the invention
The present invention is directed to the proposition of above problem, and develop a kind of neutral point clamper photovoltaic DC-to-AC converter and modulator approach thereof.
Technological means of the present invention is as follows:
A kind of neutral point clamper photovoltaic DC-to-AC converter, described photovoltaic DC-to-AC converter comprises: input connects respectively the DC-DC converter PV1 of a photovoltaic cell output and PV2, by capacitor C
dc1and C
dc2dividing potential drop branch road in series, by clamp diode D
1and D
2a phase brachium pontis neutral point clamper branch road in series, the power switch tube S being connected in series by the mode that connects successively source electrode according to draining
a1, S
a2, S
a3and S
a4form A phase brachium pontis switching branches, by clamp diode D
3and D
4b phase brachium pontis neutral point clamper branch road in series, the power switch tube S being connected in series by the mode that connects successively source electrode according to draining
b1, S
b2, S
b3and S
b4form B phase brachium pontis switching branches, by clamp diode D
5and D
6c phase brachium pontis neutral point clamper branch road in series, by connect according to drain electrode that the mode of source electrode is connected in series successively power switch tube S
c1, S
c2, S
c3and S
c4the C phase brachium pontis switching branches forming; Described A phase brachium pontis neutral point clamper branch road two ends connect respectively power switch tube S
a1source electrode and power switch tube S
a4drain electrode; Described B phase brachium pontis neutral point clamper branch road two ends connect respectively power switch tube S
b1source electrode and power switch tube S
b4drain electrode; Described C phase brachium pontis neutral point clamper branch road two ends connect respectively power switch tube S
c1source electrode and power switch tube S
c4drain electrode; Described capacitor C
dc1, C
dc2serial connection point, with described clamp diode D
1, D
2serial connection point, described clamp diode D
3, D
4serial connection point and described clamp diode D
5, D
6serial connection point be connected; Described capacitor C
dc1two ends are connected with DC-DC converter PV1 output; Described capacitor C
dc2two ends are connected with DC-DC converter PV2 output; The output voltage of described DC-DC converter PV1 and PV2 equates, and has separately independently for regulating the DC-DC controller of described output voltage;
Further, described power switch tube S
a1, S
a2, S
a3, S
a4, S
b1, S
b2, S
b3, S
b4, S
c1, S
c2, S
c3and S
c4all be integrated with the fly-wheel diode being connected in reverse parallel between drain electrode and source electrode; Described power switch tube S
a2source electrode is via filter inductance L
aconnect electrical network; Described power switch tube S
b2source electrode is via filter inductance L
bconnect electrical network; Described power switch tube S
c2source electrode is via filter inductance L
cconnect electrical network;
A modulator approach for neutral point clamper photovoltaic DC-to-AC converter described above, this modulator approach comprises the steps:
Step 1: obtain modulating required reference voltage vector according to the Closed-loop Control Strategy of photovoltaic inverter control system;
Step 2: the fundamental space vector distribution map of setting up described photovoltaic DC-to-AC converter; Described fundamental space vector comprises 1 zero vector V
0, 6 long vector V
1～V
6, 6 middle vector V
7～V
12, and 6 short vector V
13～V
18;
Step 3: the region of living according to described reference voltage vector under α β coordinate system, choose three adjacent described middle vectors and synthesize described reference voltage vector;
Step 4: the region of living according to described reference voltage vector under α β coordinate system, choose two adjacent described zero vectors of described middle vector and synthesize described reference voltage vector;
Step 5:
According to the result of step 3 and step 4, there is the least possible constraints of power switch pipe of state variation in conjunction with the same time, determine the fundamental space vector of synthetic described reference voltage vector;
Further, described step 3 specifically comprises the steps:
When the of living in region of described reference voltage vector under α β coordinate system is 0～60 °, choose middle vector V
12, V
7and V
8synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 60～120 °, choose middle vector V
7, V
8and V
9synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 120～180 °, choose middle vector V
8, V
9and V
10synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 180～240 °, choose middle vector V
9, V
10and V
11synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 240～300 °, choose middle vector V
10, V
11and V
12synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 300～360 °, choose middle vector V
11, V
12and V
7synthetic described reference voltage vector;
Further, described step 4 specifically comprises the steps:
When the of living in region of described reference voltage vector under α β coordinate system is-30～30 °, choose middle vector V
12, V
7with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 30～90 °, choose middle vector V
7, V
8with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 90～150 °, choose middle vector V
8, V
9with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 150～210 °, choose middle vector V
9, V
10with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 210～270 °, choose middle vector V
10, V
11with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 270～330 °, choose middle vector V
11, V
12with zero vector V
0synthetic described reference voltage vector;
Further, described step 5 specifically comprises the steps:
When the of living in region of described reference voltage vector under α β coordinate system is 0～30 °, determine by middle vector V
12, V
7with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 30～60 °, determine by middle vector V
12, V
7and V
8synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 60～90 °, determine by middle vector V
7, V
8with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 90～120 °, determine by middle vector V
7, V
8and V
9synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 120～150 °, determine by middle vector V
8, V
9with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 150～180 °, determine by middle vector V
8, V
9and V
10synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 180～210 °, determine by middle vector V
9, V
10with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 210～240 °, determine by middle vector V
9, V
10and V
11synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 240～270 °, determine by middle vector V
10, V
11with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 270～300 °, determine by middle vector V
10, V
11and V
12synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 300～330 °, determine by middle vector V
11, V
12with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 330～360 °, determine by middle vector V
11, V
12and V
7synthetic described reference voltage vector.
Owing to having adopted technique scheme, a kind of neutral point clamper photovoltaic DC-to-AC converter provided by the invention and modulator approach thereof, the present invention is by introducing two output voltage independent control and equal DC-DC converter respectively, the unbalanced problem of neutral point of having avoided traditional neutral point clamper photovoltaic DC-to-AC converter to adopt merely capacitance partial pressure to cause, coordinate improved modulator approach simultaneously, by Rational choice and the sequence of the power switch pipe on off sequence to fundamental space vector and correspondence thereof, make system common-mode voltage all-the-time stable in a certain normal value, effectively reduce the generation of system high-frequency common mode leakage current, it is convenient to realize, harmonic content that simultaneously can inhibition system networking electric current, improve the quality of power supply of inverter networking electric current, structure of the present invention and method are simple, almost do not change the hardware configuration of current same device, cost is lower.
Brief description of the drawings
Fig. 1 is the non-isolation type three-phase photovoltaic grid-connected inverting device circuit theory diagrams of considering parasitic parameter;
Fig. 2 is the high frequency common mode equivalent electric circuit of three-phase photovoltaic grid-connected inverting device;
Fig. 3 is the high frequency common mode equivalent electric circuit of A-B phase in three-phase photovoltaic grid-connected inverting device;
Fig. 4 is the fundamental space vector distribution map of photovoltaic DC-to-AC converter of the present invention;
Fig. 5 is the topological structure schematic diagram of neutral point clamper photovoltaic DC-to-AC converter of the present invention;
Fig. 6-a is that the on off state of traditional SVPWM modulation system is analyzed schematic diagram;
Fig. 6-b is the analysis schematic diagram of the common-mode voltage that produces of traditional SVPWM modulation system;
Fig. 7-a is that the power switch pipe on off state of carrying out after modulator approach step 3 of the present invention is analyzed schematic diagram;
Fig. 7-b is the analysis schematic diagram of carrying out the common-mode voltage of the rear generation of modulator approach step 3 of the present invention;
Fig. 8-a is that the power switch pipe on off state of carrying out after modulator approach step 4 of the present invention is analyzed schematic diagram;
Fig. 8-b is the analysis schematic diagram of carrying out the common-mode voltage of the rear generation of modulator approach step 4 of the present invention;
Fig. 9 is the circuit theory diagrams of DC-DC converter of the present invention.
Embodiment
Fig. 1 shows the non-isolation type three-phase photovoltaic grid-connected inverting device circuit theory diagrams of considering parasitic parameter, and as shown in Figure 1, described three-phase photovoltaic grid-connected inverting device comprises photovoltaic cell PV, capacitor C
dc, DC/AC module, filter inductance L
a, L
b, L
c, filter capacitor C
f1, C
f2, C
f3, series reactor L
ca, L
cb, L
cc, transmission line impedance Z
a, Z
b, Z
c, and ground impedance Z between electrical network earth point and inverter chassics earth point
g; Described DC/AC module can be full-bridge circuit, can be also multi-level inverter circuit; In Fig. 1, also show the parasitic capacitance C of photovoltaic cell to the earth
g-pv, its size depends on the factors such as material, area, soil property, air humidity and the mounting means of photovoltaic cell, and parasitic capacitance C between inverter output point and the earth
ga, C
gb, C
gc, it is mainly formed fin by the silicon chip of switching device; In the time that inverter HF switch is moved, can cause parasitic capacitance C
ga, C
gb, C
gcthe high-frequency fluctuation of upper voltage, and then produce common mode leakage current, the parasitic capacitance C of the photovoltaic cell of flowing through
g-pvhigh frequency common mode current may damage photovoltaic cell.Fig. 2 shows the high frequency common mode equivalent electric circuit of three-phase photovoltaic grid-connected inverting device, wherein, and V
aQ, V
bQ, V
cQbe respectively the voltage between the node A shown in Fig. 1 and node Q, Node B and node Q, node C and node Q; Because line voltage is low frequency signal, the common mode leakage current of its generation is very little, therefore the high frequency common mode equivalent electric circuit shown in Fig. 2 has been ignored the impact of line voltage.Further, according to Thevenin's theorem and superposition theorem, consider the impact of differential mode voltage on common-mode voltage simultaneously, described high frequency common mode equivalent electric circuit can be equivalent to three single-phase common mode equivalent models; Fig. 3 shows the high frequency common mode equivalent electric circuit of A-B phase in three-phase photovoltaic grid-connected inverting device, and the high frequency common mode equivalent electric circuit of B-C phase and C-A phase is similar with it, wherein, and V
cm-ABrepresent the common-mode voltage that A-B is alternate, be specially V
cm-AB=(V
aQ+ V
bQ) 2; V
dm-ABrepresent the differential mode voltage that A-B is alternate, be specially V
dm-AB=V
aQ-V
bQ;
l
ab=L
a//L
b; L
cab=L
ca//L
cb; Z
ab=Z
a//Z
b; Definition from common mode is further derived, and the common-mode voltage of three-phase inverter is
Ignore the unbalanced state of three-phase parasitic parameter in circuit herein, known by above-mentioned analysis, in non-isolation type photovoltaic grid-connected inversion circuit, it is the basic reason that common-mode effect produces that the high frequency of switching device changes, and the variation of the high frequency of switching device is often determined by modulator approach, therefore under this topological structure, modulation system is depended in the generation of common-mode voltage to a great extent.
A kind of neutral point clamper photovoltaic DC-to-AC converter as shown in Figure 5, described photovoltaic DC-to-AC converter comprises: input connects respectively the DC-DC converter PV1 of a photovoltaic cell output and PV2, by capacitor C
dc1and C
dc2dividing potential drop branch road in series, by clamp diode D
1and D
2a phase brachium pontis neutral point clamper branch road in series, the power switch tube S being connected in series by the mode that connects successively source electrode according to draining
a1, S
a2, S
a3and S
a4form A phase brachium pontis switching branches, by clamp diode D
3and D
4b phase brachium pontis neutral point clamper branch road in series, the power switch tube S being connected in series by the mode that connects successively source electrode according to draining
b1, S
b2, S
b3and S
b4form B phase brachium pontis switching branches, by clamp diode D
5and D
6c phase brachium pontis neutral point clamper branch road in series, by connect according to drain electrode that the mode of source electrode is connected in series successively power switch tube S
c1, S
c2, S
c3and S
c4the C phase brachium pontis switching branches forming; Described A phase brachium pontis neutral point clamper branch road two ends connect respectively power switch tube S
a1source electrode and power switch tube S
a4drain electrode; Described B phase brachium pontis neutral point clamper branch road two ends connect respectively power switch tube S
b1source electrode and power switch tube S
b4drain electrode; Described C phase brachium pontis neutral point clamper branch road two ends connect respectively power switch tube S
c1source electrode and power switch tube S
c4drain electrode; Described capacitor C
dc1, C
dc2serial connection point, with described clamp diode D
1, D
2serial connection point, described clamp diode D
3, D
4serial connection point and described clamp diode D
5, D
6serial connection point be connected; Described capacitor C
dc1two ends are connected with DC-DC converter PV1 output; Described capacitor C
dc2two ends are connected with DC-DC converter PV2 output; The output voltage of described DC-DC converter PV1 and PV2 equates, and has separately independently for regulating the DC-DC controller of described output voltage; Further, described power switch tube S
a1, S
a2, S
a3, S
a4, S
b1, S
b2, S
b3, S
b4, S
c1, S
c2, S
c3and S
c4all be integrated with the fly-wheel diode being connected in reverse parallel between drain electrode and source electrode; Described power switch tube S
a2source electrode is via filter inductance L
aconnect electrical network; Described power switch tube S
b2source electrode is via filter inductance L
bconnect electrical network; Described power switch tube S
c2source electrode is via filter inductance L
cconnect electrical network.
The present invention can be applicable to parallel network power generation field, and described photovoltaic DC-to-AC converter is non-isolation type three-phase photovoltaic grid-connected inverting device, and it comprises that input connects respectively DC-DC converter PV1 and the PV2 of a photovoltaic cell output; Described capacitor C
dc1two ends are connected with DC-DC converter PV1 output; Described capacitor C
dc2two ends are connected with DC-DC converter PV2 output; The output voltage of described DC-DC converter PV1 and PV2 equates, and has separately independently for regulating the DC-DC controller of described output voltage; Fig. 8 shows the circuit theory diagrams of DC-DC converter of the present invention, as shown in Figure 8, DC-DC converter comprises the Boost booster circuit that input is connected with photovoltaic battery array output, and this booster circuit comprises inductance L 1, switching tube S1, diode D1 and capacitor C
dc; Described DC-DC converter also comprises DC/DC controller and PWM drive circuit; Described DC-DC controller is realized the closed loop adjustment of output voltage U o according to flow through electric current I i and Boost booster circuit output voltage U o of photovoltaic battery array output voltage U i, inductance L 1, by the turn-on and turn-off of PWM drive circuit control switch pipe S1, thereby ensure that output voltage U o is constant; Photovoltaic DC-to-AC converter of the present invention is by introducing two output voltage independent control and equal DC-DC converter respectively, the unbalanced problem of neutral point of having avoided traditional neutral point clamper photovoltaic DC-to-AC converter to adopt merely capacitance partial pressure to cause.
Fig. 5 shows the topological structure schematic diagram of neutral point clamper photovoltaic DC-to-AC converter of the present invention, below for the neutral point clamper photovoltaic DC-to-AC converter Analysis of Topological Structure SVPWM space vector modulation mode after this improvement, Fig. 4 shows the fundamental space vector distribution map of photovoltaic DC-to-AC converter of the present invention, as shown in Figure 4, have 19 fundamental space vectors, comprise respectively 1 zero vector V
0, 6 long vector V
1～V
6, 6 middle vector V
7～V
12, and 6 short vector V
13～V
18, table 1 has provided reference voltage vector possible on off state and corresponding common-mode voltage during from-30～150 ° in α β coordinate system, as shown in table 1, can find out the common-mode voltage V of inverter
cMvariation with on off state changes, and owing to adopting neutral point clamper photovoltaic DC-to-AC converter topological structure of the present invention, does not have the unbalanced problem of neutral point, therefore common-mode voltage V herein
cMvalue can be with the node P in Fig. 5 and the voltage V between node Q
pQcarry out scalar, the SVPWM modulation system of analysis conventional, the situation of selecting modulation ratio to be greater than 0.5, Fig. 6-a, Fig. 6-b show respectively traditional on off state of SVPWM modulation system and the analysis schematic diagram of the common-mode voltage of generation, as shown in Fig. 6-a, Fig. 6-b, in the time that reference voltage vector is within the scope of 0～30 °, reference voltage vector is by fundamental space vector V
1, V
7and V
13form its corresponding common-mode voltage V
cMvalue be respectively V
pQ/ 3, V
pQ/ 2,2V
pQ/ 3, be not difficult to find that inverter will produce periodically variable common-mode voltage, thereby causes high frequency common mode leakage current in the continuous change procedure of reference voltage vector.
Table 1. reference voltage vector possible on off state and corresponding common-mode voltage tables of data during from-30～150 ° in α β coordinate system.
| S a1 S a2 | S a3 S a4 | S b1 S b2 | S b3 S b4 | S c1 S c2 | S c3 S c4 | Vector | Common-mode voltage V CM |
| 0 0 | 1 1 | 0 0 | 1 1 | 0 0 | 1 1 | V 0 | 0 |
| 1 1 | 0 0 | 1 1 | 0 0 | 1 1 | 0 0 | V 0 | V PQ |
| 0 1 | 1 0 | 0 1 | 1 0 | 0 1 | 1 0 | V 0 | V PQ/2 |
| 1 1 | 0 0 | 0 0 | 1 1 | 0 0 | 1 1 | V 1 | V PQ/3 |
| 1 1 | 0 0 | 1 1 | 0 0 | 0 0 | 1 1 | V 2 | 2V PQ/3 |
| 0 0 | 1 1 | 1 1 | 0 0 | 0 0 | 1 1 | V 3 | V PQ/3 |
| 1 1 | 0 0 | 0 1 | 1 0 | 0 0 | 1 1 | V 7 | V PQ/2 |
| 0 1 | 1 0 | 1 1 | 0 0 | 0 0 | 1 1 | V 8 | V PQ/2 |
| 0 0 | 1 1 | 1 1 | 0 0 | 0 1 | 1 0 | V 9 | V PQ/2 |
| 1 1 | 0 0 | 0 0 | 1 1 | 0 1 | 1 0 | V 12 | V PQ/2 |
| 0 1 | 1 0 | 0 0 | 1 1 | 0 0 | 1 1 | V 13 | V PQ/6 |
| 1 1 | 0 0 | 0 1 | 1 0 | 0 1 | 1 0 | V 13 | 2V PQ/3 |
| 0 1 | 1 0 | 0 1 | 1 0 | 0 0 | 1 1 | V 14 | V PQ/3 |
| 1 1 | 0 0 | 1 1 | 0 0 | 0 1 | 1 0 | V 14 | 5V PQ/6 |
| 0 0 | 1 1 | 0 1 | 1 0 | 0 0 | 1 1 | V 15 | V PQ/6 |
| 0 1 | 1 0 | 1 1 | 0 0 | 0 1 | 1 0 | V 15 | 2V PQ/3 |
The specific embodiments of the modulator approach of neutral point clamper photovoltaic DC-to-AC converter of the present invention is as follows:
A modulator approach for neutral point clamper photovoltaic DC-to-AC converter described above, this modulator approach comprises the steps:
Step 1: obtain modulating required reference voltage vector according to the Closed-loop Control Strategy of photovoltaic inverter control system;
Step 2: the fundamental space vector distribution map of setting up described photovoltaic DC-to-AC converter; Described fundamental space vector comprises 1 zero vector V
0, 6 long vector V
1～V
6, 6 middle vector V
7～V
12, and 6 short vector V
13～V
18;
Step 3: the region of living according to described reference voltage vector under α β coordinate system, choose three adjacent described middle vectors and synthesize described reference voltage vector;
Step 4: the region of living according to described reference voltage vector under α β coordinate system, choose two adjacent described zero vectors of described middle vector and synthesize described reference voltage vector;
Step 5:
According to the result of step 3 and step 4, there is the least possible constraints of power switch pipe of state variation in conjunction with the same time, determine the fundamental space vector of synthetic described reference voltage vector;
Further, described step 3 specifically comprises the steps: that working as the of living in region of described reference voltage vector under α β coordinate system is 0～60 °, chooses middle vector V
12, V
7and V
8synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 60～120 °, choose middle vector V
7, V
8and V
9synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 120～180 °, choose middle vector V
8, V
9and V
10synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 180～240 °, choose middle vector V
9, V
10and V
11synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 240～300 °, choose middle vector V
10, V
11and V
12synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 300～360 °, choose middle vector V
11, V
12and V
7synthetic described reference voltage vector;
Further, described step 4 specifically comprises the steps: to be-30～30 ° when the region of living in of described reference voltage vector under α β coordinate system, chooses middle vector V
12, V
7with zero vector V
0synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 30～90 °, choose middle vector V
7, V
8with zero vector V
0synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 90～150 °, choose middle vector V
8, V
9with zero vector V
0synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 150～210 °, choose middle vector V
9, V
10with zero vector V
0synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 210～270 °, choose middle vector V
10, V
11with zero vector V
0synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 270～330 °, choose middle vector V
11, V
12with zero vector V
0synthetic described reference voltage vector;
Further, described step 5 specifically comprises the steps: that working as the of living in region of described reference voltage vector under α β coordinate system is 0～30 °, determines by middle vector V
12, V
7with zero vector V
0synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 30～60 °, determine by middle vector V
12, V
7and V
8synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 60～90 °, determine by middle vector V
7, V
8with zero vector V
0synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 90～120 °, determine by middle vector V
7, V
8and V
9synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 120～150 °, determine by middle vector V
8, V
9with zero vector V
0synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 150～180 °, determine by middle vector V
8, V
9and V
10synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 180～210 °, determine by middle vector V
9, V
10with zero vector V
0synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 210～240 °, determine by middle vector V
9, V
10and V
11synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 240～270 °, determine by middle vector V
10, V
11with zero vector V
0synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 270～300 °, determine by middle vector V
10, V
11and V
12synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 300～330 °, determine by middle vector V
11, V
12with zero vector V
0synthetic described reference voltage vector; When the of living in region of described reference voltage vector under α β coordinate system is 330～360 °, determine by middle vector V
11, V
12and V
7synthetic described reference voltage vector.
There is the least possible constraints of power switch pipe of state variation in the same time of the present invention, the power switch pipe that refers to same time generation state variation is few as much as possible, and then can reduce the power loss of switching between power switch pipe conducting state and off state.
Fig. 7-a shows the power switch pipe on off state of carrying out after modulator approach step 3 of the present invention and analyzes schematic diagram; Fig. 7-b shows the analysis schematic diagram of the common-mode voltage of carrying out the rear generation of modulator approach step 3 of the present invention; As shown in Fig. 7-a, 7-b, common-mode voltage V in whole process
cMvalue be V
pQ/ 2, V
pQfor the voltage between node P and node Q in Fig. 5.
Fig. 8-a shows the power switch pipe on off state of carrying out after modulator approach step 4 of the present invention and analyzes schematic diagram; Fig. 8-b shows the analysis schematic diagram of the common-mode voltage of carrying out the rear generation of modulator approach step 4 of the present invention; As shown in Fig. 8-a, 8-b, common-mode voltage V in whole process
cMvalue be V
pQ/ 2, V
pQfor the voltage between node P and node Q in Fig. 5.
Neutral point clamper photovoltaic DC-to-AC converter topological structure of the present invention, coordinate improved modulator approach simultaneously, by Rational choice and the sequence of the Rational choice to fundamental space vector and corresponding power switch pipe on off sequence thereof, make system common-mode voltage all-the-time stable in a certain normal value, effectively reduce the generation of system high-frequency common mode leakage current, it is convenient to realize, harmonic content that simultaneously can inhibition system networking electric current, improve the quality of power supply of inverter networking electric current, structure of the present invention and method are simple, the hardware configuration that does not almost change current same device, cost is lower.
The above; it is only preferably embodiment of the present invention; but protection scope of the present invention is not limited to this; any be familiar with those skilled in the art the present invention disclose technical scope in; be equal to replacement or changed according to technical scheme of the present invention and inventive concept thereof, within all should being encompassed in protection scope of the present invention.
Claims (6)
1. a neutral point clamper photovoltaic DC-to-AC converter, is characterized in that, described photovoltaic DC-to-AC converter comprises: input connects respectively the DC-DC converter PV1 of a photovoltaic cell output and PV2, by capacitor C
dc1and C
dc2dividing potential drop branch road in series, by clamp diode D
1and D
2a phase brachium pontis neutral point clamper branch road in series, the power switch tube S being connected in series by the mode that connects successively source electrode according to draining
a1, S
a2, S
a3and S
a4form A phase brachium pontis switching branches, by clamp diode D
3and D
4b phase brachium pontis neutral point clamper branch road in series, the power switch tube S being connected in series by the mode that connects successively source electrode according to draining
b1, S
b2, S
b3and S
b4form B phase brachium pontis switching branches, by clamp diode D
5and D
6c phase brachium pontis neutral point clamper branch road in series, by connect according to drain electrode that the mode of source electrode is connected in series successively power switch tube S
c1, S
c2, S
c3and S
c4the C phase brachium pontis switching branches forming; Described A phase brachium pontis neutral point clamper branch road two ends connect respectively power switch tube S
a1source electrode and power switch tube S
a4drain electrode; Described B phase brachium pontis neutral point clamper branch road two ends connect respectively power switch tube S
b1source electrode and power switch tube S
b4drain electrode; Described C phase brachium pontis neutral point clamper branch road two ends connect respectively power switch tube S
c1source electrode and power switch tube S
c4drain electrode; Described capacitor C
dc1, C
dc2serial connection point, with described clamp diode D
1, D
2serial connection point, described clamp diode D
3, D
4serial connection point and described clamp diode D
5, D
6serial connection point be connected; Described capacitor C
dc1two ends are connected with DC-DC converter PV1 output; Described capacitor C
dc2two ends are connected with DC-DC converter PV2 output; The output voltage of described DC-DC converter PV1 and PV2 equates, and has separately independently for regulating the DC-DC controller of described output voltage.
2. a kind of neutral point clamper photovoltaic DC-to-AC converter according to claim 1, is characterized in that: described power switch tube S
a1, S
a2, S
a3, S
a4, S
b1, S
b2, S
b3, S
b4, S
c1, S
c2, S
c3and S
c4all be integrated with the fly-wheel diode being connected in reverse parallel between drain electrode and source electrode; Described power switch tube S
a2source electrode is via filter inductance L
aconnect electrical network; Described power switch tube S
b2source electrode is via filter inductance L
bconnect electrical network; Described power switch tube S
c2source electrode is via filter inductance L
cconnect electrical network.
3. a modulator approach for neutral point clamper photovoltaic DC-to-AC converter as claimed in claim 1, is characterized in that, this modulator approach comprises the steps:
Step 1: obtain modulating required reference voltage vector according to the Closed-loop Control Strategy of photovoltaic inverter control system;
Step 2: the fundamental space vector distribution map of setting up described photovoltaic DC-to-AC converter; Described fundamental space vector comprises 1 zero vector V
0, 6 long vector V
1～V
6, 6 middle vector V
7～V
12, and 6 short vector V
13～V
18;
Step 3: the region of living according to described reference voltage vector under α β coordinate system, choose three adjacent described middle vectors and synthesize described reference voltage vector;
Step 4: the region of living according to described reference voltage vector under α β coordinate system, choose two adjacent described zero vectors of described middle vector and synthesize described reference voltage vector;
Step 5:
According to the result of step 3 and step 4, there is the least possible constraints of power switch pipe of state variation in conjunction with the same time, determine the fundamental space vector of synthetic described reference voltage vector.
4. the modulator approach of neutral point clamper photovoltaic DC-to-AC converter according to claim 3, is characterized in that described step 3 specifically comprises the steps:
When the of living in region of described reference voltage vector under α β coordinate system is 0～60 °, choose middle vector V
12, V
7and V
8synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 60～120 °, choose middle vector V
7, V
8and V
9synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 120～180 °, choose middle vector V
8, V
9and V
10synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 180～240 °, choose middle vector V
9, V
10and V
11synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 240～300 °, choose middle vector V
10, V
11and V
12synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 300～360 °, choose middle vector V
11, V
12and V
7synthetic described reference voltage vector.
5. the modulator approach of neutral point clamper photovoltaic DC-to-AC converter according to claim 3, is characterized in that described step 4 specifically comprises the steps:
When the of living in region of described reference voltage vector under α β coordinate system is-30～30 °, choose middle vector V
12, V
7with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 30～90 °, choose middle vector V
7, V
8with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 90～150 °, choose middle vector V
8, V
9with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 150～210 °, choose middle vector V
9, V
10with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 210～270 °, choose middle vector V
10, V
11with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 270～330 °, choose middle vector V
11, V
12with zero vector V
0synthetic described reference voltage vector.
6. the modulator approach of neutral point clamper photovoltaic DC-to-AC converter according to claim 3, is characterized in that described step 5 specifically comprises the steps:
When the of living in region of described reference voltage vector under α β coordinate system is 0～30 °, determine by middle vector V
12, V
7with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 30～60 °, determine by middle vector V
12, V
7and V
8synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 60～90 °, determine by middle vector V
7, V
8with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 90～120 °, determine by middle vector V
7, V
8and V
9synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 120～150 °, determine by middle vector V
8, V
9with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 150～180 °, determine by middle vector V
8, V
9and V
10synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 180～210 °, determine by middle vector V
9, V
10with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 210～240 °, determine by middle vector V
9, V
10and V
11synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 240～270 °, determine by middle vector V
10, V
11with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 270～300 °, determine by middle vector V
10, V
11and V
12synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 300～330 °, determine by middle vector V
11, V
12with zero vector V
0synthetic described reference voltage vector;
When the of living in region of described reference voltage vector under α β coordinate system is 330～360 °, determine by middle vector V
11, V
12and V
7synthetic described reference voltage vector.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107078663A (en) * | 2014-11-28 | 2017-08-18 | 罗伯特·博世有限公司 | The battery pack system for the NPC inverter being connected with hybrid battery group and in input side with battery pack and the method for operating in the NPC inverter that input side is connected with hybrid battery group |
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