CN106253733A - Two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking - Google Patents

Abstract

The present invention discloses a kind of two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking, and including selecting Switch State Combination in Power Systems, described method includes: write out all 16 kinds of on off state S of two H bridge cascaded inverters_1a/S_1b/S_2a/S_2bAnd calculate photovoltaic cell parasitic capacitor voltage sum V of correspondence_cValue；According to maintaining photovoltaic cell parasitic capacitor voltage sum V_cFor V_dcRequirement, select meet requirement on off state；Carry out producing PWM drive waveforms.The method can not only suppression system leakage current effectively, and extend conveniently, the suitability is strong, low cost.

Description

Two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking

Technical field

The invention belongs to the photovoltaic power generation technology in electrical engineering field, more particularly, it relates to one is hung down based on modified model Two H bridge photovoltaic inverter leakage current suppressing method of straight carrier wave stacking modulation strategy.

Background technology

Compared with conventional inverter, cascaded H-bridges multi-electrical level inverter has that grid current harmonic is little, switching frequency is low, filter Ripple body amasss little and is prone to the advantages such as modularity, has therefore obtained the concern of more and more scholar.

Additionally, the DC side of each module of cascaded H-bridges multi-electrical level inverter can be independently-powered by one piece of photovoltaic panel so that it is solely Vertical MPPT controls to be possibly realized, and therefore cascaded H-bridges many level topological structure is particularly suited for photovoltaic combining inverter.

Due to cascaded H-bridges inverter module structure, grid-connected required voltage can be reached by cascading certain quantity, Therefore can save the transformator of raising voltage and buffer action, reduce cost further and improve power density.

But, owing to lacking transformer isolation, between photovoltaic panel and electrical network, there is directly electrical connection, can be in photovoltaic panel And in the parasitic capacitance between the earth, producing leakage current, leakage current can affect the efficiency of system, reduce system reliability, threat people The safety of body and generation electromagnetic interference etc., be therefore highly desirable to suppress leakage current.

At present, traditional drain current suppressing method can be largely classified into following three kinds: 1) use the topological structure improved, as The topologys such as H5, H6；2) passive filter is used, such as common mode inductance, electromagnetic interface filter etc.；3) suitable modulation strategy is sought.

But, unlike single module inverter topology, the composition of cascaded H-bridges topology leakage current not only with this module Output is relevant, and the also output with other modules of cascade is associated.Therefore, the suppressing method of single H bridge leakage current can not be straight Connect the suppression applying to cascaded H-bridges topology leakage current, cause method and the level of existing single module inverter suppression leakage current A little mismatch is there is between connection H bridge inverter drain current suppressing method.

To this end, scholars have done a lot of effort and trial in terms of the drain current suppressing of cascaded H-bridges inverter, such as 2016 IEEE document " Single Phase Cascaded H5 Inverter with Leakage Current Elimination For Transformerless Photovoltaic System " (" non-isolation type Cascade H 5 photovoltaic DC-to-AC converter common mode current is special Property analyze " 2016 years IEEE energy sciences can plenary session collection of thesis) and propose a kind of about Cascade H 5 topology suppression electric leakage The modulation strategy of stream, although inhibit leakage current to a certain extent, but be as number of modules and increase modulation strategy and can answer very much Miscellaneous, it is unfavorable for system extension and modularized design, and modulation strategy is complicated.Additionally, Cascade H 5 topology proposed is compared H4 and is opened up Flutterring, cost and loss all can increase.

IEEE document " Analysis and Suppression of Leakage Current in 2014 Cascaded-Multilevel–Inverter-Based PV Systems,”Y.Zhou and H.Li,《IEEE Trans.Power Electron. ", 2014,29 (10), 5,265 5277 (" cascade connection multi-level photovoltaic inverter leakage current analyses With suppression ", " IEEE journal-power electronics periodical ", volume 29 the 10th phase page 5,265 5277 in 2014) propose at DC side Add common-mode filter suppression leakage current with AC respectively, but its switching frequency is set as 10kHz, this and use cascaded topology The original intention reducing switching frequency does not meets.

IEEE document " A Modulation Strategy for Single-phase HB-CMI in 2013 Reduce Leakage Ground Current in Transformer-less PV Applications " (" cascade is the most electric Flat photovoltaic inverter leakage current analysis and suppression " 2013 years IEEE energy sciences can plenary session collection of thesis) modulation that proposes Strategy makes parasitic capacitor voltage change by power frequency staircase waveform, but this modulation strategy is relatively complicated and is not easy to system extension.

Document " Hybrid Multicarrier Modulation to Reduce Leakage Current in a Transformer-less Cascaded Multilevel Inverter for Photovoltaic Systems” Rajasekar Selvamuthukumaran,AbhishekGarg,and Rajesh Gupta.《IEEE Transactions On Power Electronics ", 2015,30 (4): 1779-1783 (" for non-isolation type cascaded multilevel inverter photovoltaic The mixing multi-carrier modulation strategy of system ", " IEEE journal-power electronics periodical ", the 4th phase 1,779 1783 of volume 30 in 2015 Page) POD (the Phase Opposite Disposition) modulation strategy of a kind of correction is proposed, it is proposed that in common-mode voltage amplitude The principle of action when change is minimum, but by this modulation strategy imperfection, its common-mode voltage obtained still suffers from high fdrequency component, and Not operatively suppress the leakage current of cascaded H-bridges.

In sum, for single-phase non-isolated cascaded H-bridges photovoltaic DC-to-AC converter, existing drain current suppressing method is mainly deposited In following problem:

(1) use the topology improved, such as H5 and H6, cost and the loss of system can be increased, reduce inverter efficiency and Power density；

(2) method adding common-mode filter respectively in inverter ac side and DC side is used, although can be necessarily Suppressing leakage current in degree, but leakage current harmonic spectrum is abundanter, filter parameter design is complex.Additionally, use filtering Device also can increase volume and the cost of system.

Summary of the invention

The technical problem to be solved in the present invention is exactly the limitation overcoming above-mentioned various scheme, inverse for non-isolation type photovoltaic Become device produces leakage current owing to lacking transformer isolation problem in parasitic capacitance between photovoltaic panel and the earth, it is proposed that Two H bridge photovoltaic inverter leakage current suppressing method based on improved vertical carrier wave stacking modulation strategy, the method has extension Convenient, calculate the advantages such as simple and low cost.

For solving the technical problem of the present invention, the technical scheme key step used is as follows:

A kind of two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking, including selecting switch shape State combines, and key step is as follows:

Step 1, if two module DC voltages of two H bridge cascaded inverters are identical, and is designated as V_dc, calculate two H bridges All 16 kinds of on off state S of cascaded inverter_1a/S_1b/S_2a/S_2bCorresponding photovoltaic cell parasitic capacitor voltage sum V_cValue,

V_c=V_dc(S_1a+S_2b)

Wherein, S_1aIt is the switch function of pipe, S on first left brachium pontis of H bridge_1bIt it is the switch of pipe on first right brachium pontis of H bridge Function, S_2aIt is the switch function of pipe, S on second left brachium pontis of H bridge_2bIt is the switch function of pipe on second right brachium pontis of H bridge, and Meet:

Each switch function S_1a、S_1b、S_2a、S_2bValue all include 0 and 1 two states, the value of switch function is arranged Group is incorporated as on off state S_1a/S_1b/S_2a/S_2bValue, totally 2⁴Kind, i.e. this 2⁴The value planting on off state is exactly two H bridges cascades The all of 16 kinds of on off state S of inverter_1a/S_1b/S_2a/S_2b；

Step 2, according to all 16 kinds of on off states of two H bridge cascaded inverters that step 1 is write out, according to maintaining photovoltaic Battery parasitic capacitance voltage sum V_cEqual to V_dcRequirement, select meet requirement on off state, composition following two switch shape State combines:

The first Switch State Combination in Power Systems: 1010-1000-1100-0011-0001-0101

The second Switch State Combination in Power Systems: 1010-1110-1100-0011-0111-0101

Above two Switch State Combination in Power Systems comprises 6 kinds of on off states respectively；

Step 3, two kinds of Switch State Combination in Power Systems that step 2 is obtained, respectively selection following methods generation PWM drive signal:

The first Switch State Combination in Power Systems, it is achieved method be modulating wave and four adjacent between the most anti-phase triangular carrier enter Go to compare and obtain PWM drive signal；

The second Switch State Combination in Power Systems, it is achieved method be modulating wave and four adjacent between the most anti-phase triangular carrier enter Go to compare and obtain PWM drive signal.

Preferably, the implementation method of the first Switch State Combination in Power Systems in step 2 is:

At the positive half period of modulating wave, on off state 1010 represents that output voltage is 2V_dc, on off state 1000 represents output Voltage is V_dc, on off state 1100 represents that output voltage is 0；

At the negative half-cycle of modulating wave, on off state 0011 represents that output voltage is 0, and on off state 0001 represents output electricity Pressure is-V_dc, on off state 0101 represents that output voltage is-2V_dc；

On off state 0011 switches at modulating wave zero crossing with 1100.

Preferably, the implementation method of the second Switch State Combination in Power Systems in step 2 is:

At the positive half period of modulating wave, on off state 1010 represents that output voltage is 2V_dc, on off state 1110 represents output Voltage is V_dc, on off state 1100 represents that output voltage is 0；

At the negative half-cycle of modulating wave, on off state 0011 represents that output voltage is 0, and on off state 0111 represents output electricity Pressure is-V_dc, on off state 0101 represents that output voltage is-2V_dc；

On off state 0011 switches at modulating wave zero crossing with 1100.

Preferably, the PWM drive signal producing method of the first Switch State Combination in Power Systems described in step 3 is:

(1) as modulating wave C_refWhen >=1, S_1a=1, S_2b=0；S_1bBy modulating wave C_refCompare with triangular carrier car3 and obtain, Work as C_ref> car3 time, S_1b=0, otherwise, S_2a=1；S_2aBy modulating wave C_refCompare with triangular carrier car4 and obtain, work as C_ref>car4 Time, S_2a=1, otherwise, S_2a=0；

(2) as modulating wave C_ref< when 1, then S_1a=0, S_2b=1；S_1bBy modulating wave C_refCompare with triangular carrier car2 Arrive, if C_ref> car2, S_1b=0, otherwise, S_1b=1；S_2aBy modulating wave C_refCompare with triangular carrier car1 and obtain, if C_ref> Car1, S_2a=1, otherwise, S_2a=0；

Wherein, S_1aIt is the switch function of pipe, S on first left brachium pontis of H bridge_1bIt it is the switch of pipe on first right brachium pontis of H bridge Function, S_2aIt is the switch function of pipe, S on second left brachium pontis of H bridge_2bIt it is the switch function of pipe on second right brachium pontis of H bridge；Four Between individual triangular carrier car1, car2, car3 and car4 are adjacent the most anti-phase, meet car4 > car3 > car1 > car2, and be positioned at The symmetric position of 0 coordinate axes, i.e. triangular carrier car4 and car3 are positioned on 0 coordinate axes, and triangular carrier car1 and car2 is positioned at 0 Under coordinate axes；Modulating wave Cref is the sine wave on the basis of 0.

Preferably, the PWM drive signal producing method of the second Switch State Combination in Power Systems described in step 3 is:

(1) as modulating wave C_refWhen >=1, S_1a=1, S_2b=0；S_1bBy modulating wave C_refCompare with triangular carrier car4 and obtain, Work as C_ref> car4 time, S_1b=0, otherwise, S_2a=1；S_2aBy modulating wave C_refCompare with triangular carrier car3 and obtain, work as C_ref>car3 Time, S_2a=1, otherwise, S_2a=0；

(2) as modulating wave C_ref< when 1, then S_1a=0, S_2b=1；S_1bBy modulating wave C_refCompare with triangular carrier car1 Arrive, if C_ref> car1, S_1b=0, otherwise, S_1b=1；S_2aBy modulating wave C_refCompare with triangular carrier car2 and obtain, if C_ref> Car2, S_2a=1, otherwise, S_2a=0；

Wherein, S_1aIt is the switch function of pipe, S on first left brachium pontis of H bridge_1bIt it is the switch of pipe on first right brachium pontis of H bridge Function, S_2aIt is the switch function of pipe, S on second left brachium pontis of H bridge_2bIt it is the switch function of pipe on second right brachium pontis of H bridge；Four Between individual triangular carrier car1, car2, car3 and car4 are adjacent the most anti-phase, meet car4 > car3 > car1 > car2, and be positioned at The symmetric position of 0 coordinate axes, i.e. triangular carrier car4 and car3 are positioned on 0 coordinate axes, and triangular carrier car1 and car2 is positioned at 0 Under coordinate axes；Modulating wave Cref is the sine wave on the basis of 0.

The present invention relative to the advantage of prior art is:

1, need not, by changing existing topology or using new topology such as H5 etc., be possible not only to the cost of reduction system And switching loss, and the power density of inverter can be improved.

2, need not adding common-mode filter respectively in inverter ac side and DC side, it is to avoid the fiber crops of parameter designing Tired.

Accompanying drawing explanation

Fig. 1 is the method flow diagram of the present invention.

Fig. 2 is the single-phase cascaded H-bridges photovoltaic DC-to-AC converter topological structure containing two H bridges.

Fig. 3 is the equivalent circuit of the single-phase cascaded H-bridges photovoltaic DC-to-AC converter containing two H bridges.

Fig. 4 is the first switch combination realization figure.

Fig. 5 is the second switch combination realization figure.

Detailed description of the invention

In order to make the purpose of the present invention, technical scheme and advantage clearer, below in conjunction with the accompanying drawings and embodiment, right The present invention makees the most clearly and completely to describe.

Two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking disclosed by the invention, it is adaptable to The leakage current of the tandem photovoltaic inverter of two H bridges of suppression.

Fig. 2 is the photovoltaic DC-to-AC converter topological structure of two H bridge module cascades.Wherein, parameter C_pvk1And C_pvk1(k=1,2) it is Photovoltaic panel parasitic capacitance over the ground, the external factor such as this capacitance size and the area of photovoltaic panel and weather is relevant, forms first The power switch pipe of individual H bridge is: S₁₁、S₁₂、S₁₃And S₁₄, the power switch pipe of second H bridge of composition is: S₂₁、S₂₂、S₂₃And S₂₄, L₁And L₂For net side filter inductance；v_gFor line voltage, O point is point of common coupling.

Fig. 3 is the equivalent circuit of single-phase two H bridge module cascaded H-bridges shown in Fig. 1, and wherein VC1 is parasitic capacitance C_pv1Electricity Pressure, VC2 is parasitic capacitance C_pv2Voltage, the present embodiment is analyzed as a example by power network current positive half period, and remember net side filtering Inductance L₁=L₂, voltage be V_L。

For the single-phase cascaded H-bridges photovoltaic DC-to-AC converter of shown in Fig. 2 two H bridges, disclosed by the invention based on modified model carrier wave The basic step of two H bridge photovoltaic inverter leakage current suppressing method of stacking sees Fig. 1, comprises the steps:

Step 1, if two module DC voltages of two H bridge cascaded inverters are identical, and is designated as V_dc, calculate two H bridges All 16 kinds of on off state S of cascaded inverter_1a/S_1b/S_2a/S_2bCorresponding photovoltaic cell parasitic capacitor voltage sum V_cValue, It is shown below:

V_c=V_dc(S_1a+S_2b)

Wherein, S_1aIt is the switch function of pipe, S on first left brachium pontis of H bridge_1bIt it is the switch of pipe on first right brachium pontis of H bridge Function, S_2aIt is the switch function of pipe, S on second left brachium pontis of H bridge_2bIt is the switch function of pipe on second right brachium pontis of H bridge, and Meet:

Each switch function S_1a、S_1b、S_2a、S_2bValue all include 0 and 1 two states, the value of switch function is arranged Group is incorporated as on off state S_1a/S_1b/S_2a/S_2bValue, totally 2⁴Kind, i.e. this 2⁴The value planting on off state is exactly two H bridges cascades The all of 16 kinds of on off state S of inverter_1a/S_1b/S_2a/S_2b。

V_cFormula proving as follows.

According to Fig. 3, can be able to be obtained by Kirchhoff's second law, parasitic capacitor voltage V_ckMeet following formula:

$\left\{\begin{array}{c}-V_{1a}+V_L+V_g+V_{c1}=0\\ -V_{2b}-V_L+V_{c2}=0\\ -V_{1b}+V_{2a}-V_{c2}+V_{c1}=0\end{array}\right.$

Wherein V_1a、V_1b、V_2a、V_2bIt is respectively the output terminals A of two each brachium pontis of module₁、B₁、A₂And B₂Voltage.

After arrangement, calculate parasitic capacitor voltage V_ckMeet following formula:

$V_{ck}=\underset{i=1}{\overset{k-1}{\&Sigma;}}\frac{V_{DMi}}{2}+V_{CMk}-\underset{i=k+1}{\overset{4}{\&Sigma;}}\frac{V_{DMi}}{2}$

Wherein, V_CMkAnd V_DMkRepresent common-mode voltage and the differential mode voltage of kth (k=1,2) individual module respectively；

According to the most defined switch function S_1a、S_1b、S_2a、S_2b, calculate the output terminals A of two each brachium pontis of module₁、B₁、A₂ And B₂Voltage V_1a、V_1b、V_2aAnd V_2bValue,

V_1a=S_1aV_dc,

V_1b=S_1bV_dc,

V_2a=S_2aV_dc,

V_2b=S_2bV_dc,

Finally, according to system parasitic capacitance voltage V obtained above_ckAnd the output terminals A of two each brachium pontis of module₁、B₁、 A₂And B₂Voltage V_1a、V_1b、V_2aAnd V_2bValue, calculate voltage sum V of two module H bridge cascaded inverter parasitic capacitances_c Value,

V_c=V_dc(S_1a+S_2b)

By the 16 kinds of on off state S write out_1a/S_1b/S_2a/S_2bIt is calculated 16 kinds of photovoltaic cell parasitic capacitor voltage sums V_c。

Step 2, according to all 16 kinds of on off states of two H bridge cascaded inverters that step 1 is write out, according to maintaining photovoltaic Battery parasitic capacitance voltage sum V_cEqual to V_dcRequirement, select meet requirement on off state, as shown in table 1, below composition Two kinds of Switch State Combination in Power Systems:

The first Switch State Combination in Power Systems: 1010-1000-1100-0011-0001-0101

The second Switch State Combination in Power Systems: 1010-1110-1100-0011-0111-0101

Above two Switch State Combination in Power Systems comprises following 6 kinds of on off states respectively；

The on off state of 1 four modules of table and parasitic capacitor voltage sum

Wherein, the implementation method of two kinds of Switch State Combination in Power Systems is as follows:

The first Switch State Combination in Power Systems: at the positive half period of modulating wave, on off state 1010 represents that output voltage is 2V_dc, On off state 1000 represents that output voltage is V_dc, on off state 1100 represents that output voltage is 0；At the negative half-cycle of modulating wave, On off state 0011 represents that output voltage is 0, and on off state 0001 represents that output voltage is-V_dc, on off state 0101 represents defeated Going out voltage is-2V_dc；On off state 0011 switches at modulating wave zero crossing with 1100.

The second Switch State Combination in Power Systems: at the positive half period of modulating wave, on off state 1010 represents that output voltage is 2V_dc, On off state 1110 represents that output voltage is V_dc, on off state 1100 represents that output voltage is 0；At the negative half-cycle of modulating wave, On off state 0011 represents that output voltage is 0, and on off state 0111 represents that output voltage is-V_dc, on off state 0101 represents defeated Going out voltage is-2V_dc, on off state 0011 switches at modulating wave zero crossing with 1100.

Step 3, two kinds of Switch State Combination in Power Systems that step 2 is obtained, respectively selection following methods generation PWM drive signal:

The first Switch State Combination in Power Systems, it is achieved method be modulating wave and four adjacent between the most anti-phase triangular carrier enter Go to compare and obtain PWM drive signal；

The second Switch State Combination in Power Systems, it is achieved method be modulating wave and four adjacent between the most anti-phase triangular carrier enter Go to compare and obtain PWM drive signal.

The PWM drive signal producing method of the first Switch State Combination in Power Systems is:

(1) as modulating wave C_refWhen >=1, S_1a=1, S_2b=0；S_1bBy modulating wave C_refCompare with triangular carrier car3 and obtain, Work as C_ref> car3 time, S_1b=0, otherwise, S_2a=1；S_2aBy modulating wave C_refCompare with triangular carrier car4 and obtain, work as C_ref>car4 Time, S_2a=1, otherwise, S_2a=0；

(2) as modulating wave C_ref< when 1, then S_1a=0, S_2b=1；S_1bBy modulating wave C_refCompare with triangular carrier car2 Arrive, if C_ref> car2, S_1b=0, otherwise, S_1b=1；S_2aBy modulating wave C_refCompare with triangular carrier car1 and obtain, if C_ref> Car1, S_2a=1, otherwise, S_2a=0；

Wherein, S_1aIt is the switch function of pipe, S on first left brachium pontis of H bridge_1bIt it is the switch of pipe on first right brachium pontis of H bridge Function, S_2aIt is the switch function of pipe, S on second left brachium pontis of H bridge_2bIt is the switch function of pipe on second right brachium pontis of H bridge, its In, S_1aIt is the switch function of pipe, S on first left brachium pontis of H bridge_1bIt is the switch function of pipe, S on first right brachium pontis of H bridge_2aFor The switch function of pipe, S on second left brachium pontis of H bridge_2bIt it is the switch function of pipe on second right brachium pontis of H bridge；Four triangular carriers Between car1, car2, car3 and car4 are adjacent the most anti-phase, meet car4 > car3 > car1 > car2, and be positioned at 0 coordinate axes Symmetric position, i.e. triangular carrier car4 and car3 are positioned on 0 coordinate axes, triangular carrier car1 and car2 be positioned at 0 coordinate axes it Under.Modulating wave Cref is the sine wave on the basis of 0.

Implementation method and the PWM drive signal producing method of the first Switch State Combination in Power Systems can be found in Fig. 4.

The PWM drive signal producing method of the second Switch State Combination in Power Systems is:

(1) as modulating wave C_refWhen >=1, S_1a=1, S_2b=0；S_1bBy modulating wave C_refCompare with triangular carrier car4 and obtain, Work as C_ref> car4 time, S_1b=0, otherwise, S_2a=1；S_2aBy modulating wave C_refCompare with triangular carrier car3 and obtain, work as C_ref>car3 Time, S_2a=1, otherwise, S_2a=0；

(2) as modulating wave C_ref< when 1, then S_1a=0, S_2b=1；S_1bBy modulating wave C_refCompare with triangular carrier car1 Arrive, if C_ref> car1, S_1b=0, otherwise, S_1b=1；S_2aBy modulating wave C_refCompare with triangular carrier car2 and obtain, if C_ref> Car2, S_2a=1, otherwise, S_2a=0；

Wherein, S_1aIt is the switch function of pipe, S on first left brachium pontis of H bridge_1bIt it is the switch of pipe on first right brachium pontis of H bridge Function, S_2aIt is the switch function of pipe, S on second left brachium pontis of H bridge_2bIt is the switch function of pipe on second right brachium pontis of H bridge, its In, S_1aIt is the switch function of pipe, S on first left brachium pontis of H bridge_1bIt is the switch function of pipe, S on first right brachium pontis of H bridge_2aFor The switch function of pipe, S on second left brachium pontis of H bridge_2bIt it is the switch function of pipe on second right brachium pontis of H bridge；Four triangular carriers Between car1, car2, car3 and car4 are adjacent the most anti-phase, meet car4 > car3 > car1 > car2, and be positioned at 0 coordinate axes Symmetric position, i.e. triangular carrier car4 and car3 are positioned on 0 coordinate axes, triangular carrier car1 and car2 be positioned at 0 coordinate axes it Under.Modulating wave Cref is the sine wave on the basis of 0.

Implementation method and the PWM drive signal producing method of the second Switch State Combination in Power Systems can be found in Fig. 4.

Unlike existing modulation technique, the two H bridge photovoltaic inversion based on modified model carrier wave stacking that the present invention proposes Device drain current suppressing method, according to above-mentioned steps, can maintain photovoltaic cell parasitic capacitor voltage sum is constant, thus realizes level Connection H bridge photovoltaic inverter leakage current suppression.

Two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking disclosed by the invention are applied to two The tandem photovoltaic grid-connected system of individual H bridge.Based on embodiments of the invention, those skilled in the art is not making creative labor The other embodiments obtained on the premise of Dong, all should belong to the protection domain of this patent.

Claims (5)

1. two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking, including selecting Switch State Combination in Power Systems, It is characterized in that, key step is as follows:

Step 1, if two module DC voltages of two H bridge cascaded inverters are identical, and is designated as V_dc, calculate two H bridge cascades All 16 kinds of on off state S of inverter_1a/S_1b/S_2a/S_2bCorresponding photovoltaic cell parasitic capacitor voltage sum V_cValue, as follows Formula:

V_c=V_dc(S_1a+S_2b)

Wherein, S_1aIt is the switch function of pipe, S on first left brachium pontis of H bridge_1bIt is the switch function of pipe on first right brachium pontis of H bridge, S_2aIt is the switch function of pipe, S on second left brachium pontis of H bridge_2bIt is the switch function of pipe on second right brachium pontis of H bridge, and meets:

Each switch function S_1a、S_1b、S_2a、S_2bValue all include 0 and 1 two states, the value of switch function is carried out permutation and combination And as on off state S_1a/S_1b/S_2a/S_2bValue, totally 2⁴Kind, i.e. this 2⁴The value planting on off state is exactly two H bridges cascade inversions The all of 16 kinds of on off state S of device_1a/S_1b/S_2a/S_2b；

Step 2, according to all 16 kinds of on off states of two H bridge cascaded inverters that step 1 is write out, according to maintaining photovoltaic cell Parasitic capacitor voltage sum V_cEqual to V_dcRequirement, select meet requirement on off state, form following two on off state group Close:

The first Switch State Combination in Power Systems: 1010-1000-1100-0011-0001-0101

The second Switch State Combination in Power Systems: 1010-1110-1100-0011-0111-0101

Above two Switch State Combination in Power Systems comprises 6 kinds of on off states respectively；

Step 3, two kinds of Switch State Combination in Power Systems that step 2 is obtained, respectively selection following methods generation PWM drive signal:

The first Switch State Combination in Power Systems, it is achieved method be modulating wave and four adjacent between the most anti-phase triangular carrier compare Relatively obtain PWM drive signal；

The second Switch State Combination in Power Systems, it is achieved method be modulating wave and four adjacent between the most anti-phase triangular carrier compare Relatively obtain PWM drive signal.

Two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking the most according to claim 1, its Being characterised by, the implementation method of the first Switch State Combination in Power Systems in step 2 is:

At the positive half period of modulating wave, on off state 1010 represents that output voltage is 2V_dc, on off state 1000 represents output voltage For V_dc, on off state 1100 represents that output voltage is 0；

At the negative half-cycle of modulating wave, on off state 0011 represents that output voltage is 0, and on off state 0001 represents output voltage For-V_dc, on off state 0101 represents that output voltage is-2V_dc；

On off state 0011 switches at modulating wave zero crossing with 1100.

Two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking the most according to claim 1, its Being characterised by, the implementation method of the second Switch State Combination in Power Systems in step 2 is:

At the positive half period of modulating wave, on off state 1010 represents that output voltage is 2V_dc, on off state 1110 represents output voltage For V_dc, on off state 1100 represents that output voltage is 0；

At the negative half-cycle of modulating wave, on off state 0011 represents that output voltage is 0, and on off state 0111 represents output voltage For-V_dc, on off state 0101 represents that output voltage is-2V_dc；

On off state 0011 switches at modulating wave zero crossing with 1100.

Two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking the most according to claim 1, its Being characterised by, the PWM drive signal producing method of the first Switch State Combination in Power Systems described in step 3 is:

(1) as modulating wave C_refWhen >=1, S_1a=1, S_2b=0；S_1bBy modulating wave C_refCompare with triangular carrier car3 and obtain, when C_ref> car3 time, S_1b=0, otherwise, S_2a=1；S_2aBy modulating wave C_refCompare with triangular carrier car4 and obtain, work as C_ref>car4 Time, S_2a=1, otherwise, S_2a=0；

(2) as modulating wave C_ref< when 1, then S_1a=0, S_2b=1；S_1bBy modulating wave C_refCompare with triangular carrier car2 and obtain, if C_ref> car2, S_1b=0, otherwise, S_1b=1；S_2aBy modulating wave C_refCompare with triangular carrier car1 and obtain, if C_ref> car1, S_2a =1, otherwise, S_2a=0；

Wherein, S_1aIt is the switch function of pipe, S on first left brachium pontis of H bridge_1bIt is the switch function of pipe on first right brachium pontis of H bridge, S_2aIt is the switch function of pipe, S on second left brachium pontis of H bridge_2bIt it is the switch function of pipe on second right brachium pontis of H bridge；Four triangles Between carrier wave car1, car2, car3 and car4 are adjacent the most anti-phase, meet car4 > car3 > car1 > car2, and be positioned at 0 coordinate The symmetric position of axle, i.e. triangular carrier car4 and car3 are positioned on 0 coordinate axes, and triangular carrier car1 and car2 is positioned at 0 coordinate Under axle；Modulating wave Cref is the sine wave on the basis of 0.

Two H bridge photovoltaic inverter leakage current suppressing method based on modified model carrier wave stacking the most according to claim 1, its Being characterised by, the PWM drive signal producing method of the second Switch State Combination in Power Systems described in step 3 is:

(1) as modulating wave C_refWhen >=1, S_1a=1, S_2b=0；S_1bBy modulating wave C_refCompare with triangular carrier car4 and obtain, when C_ref> car4 time, S_1b=0, otherwise, S_2a=1；S_2aBy modulating wave C_refCompare with triangular carrier car3 and obtain, work as C_ref>car3 Time, S_2a=1, otherwise, S_2a=0；

(2) as modulating wave C_ref< when 1, then S_1a=0, S_2b=1；S_1bBy modulating wave C_refCompare with triangular carrier car1 and obtain, if C_ref> car1, S_1b=0, otherwise, S_1b=1；S_2aBy modulating wave C_refCompare with triangular carrier car2 and obtain, if C_ref> car2, S_2a =1, otherwise, S_2a=0；

Wherein, S_1aIt is the switch function of pipe, S on first left brachium pontis of H bridge_1bIt is the switch function of pipe on first right brachium pontis of H bridge, S_2aIt is the switch function of pipe, S on second left brachium pontis of H bridge_2bIt it is the switch function of pipe on second right brachium pontis of H bridge；Four triangles Between carrier wave car1, car2, car3 and car4 are adjacent the most anti-phase, meet car4 > car3 > car1 > car2, and be positioned at 0 coordinate The symmetric position of axle, i.e. triangular carrier car4 and car3 are positioned on 0 coordinate axes, and triangular carrier car1 and car2 is positioned at 0 coordinate Under axle；Modulating wave Cref is the sine wave on the basis of 0.