CN103812134B - Suppression method and system for exciting current of inverter and power grid connection momentary transformer - Google Patents

Abstract

The invention discloses a suppression method and system for the exciting current of an inverter and power grid connection momentary transformer. The method mainly comprises the following steps: starting an inverter and setting the output reference value of the inverter in a synchronous rotating coordinate system as zero; detecting inverter output voltage and power grid voltage converted onto the secondary side of a delta/gamma transformer; converting the detected inverter output voltage converted onto the secondary side of the delta/gamma transformer from a three-phase static coordinate system to a two-phase synchronous rotating coordinate system to obtain ud and uq; converting the detected power grid voltage from a three-phase static coordinate system to a two-phase synchronous rotating coordinate system to obtain vd and vq, wherein when the inverter works till ud is equal to vd and uq is equal to vq, alternating-current voltages at the two ends of a grid-connected switch are synchronous before actuation of the grid-connected switch. By adopting the suppression method and the system for the exciting current of the inverter and power grid connection momentary transformer, the advantages of low hardware cost, low energy consumption and high energy conversion efficiency can be realized.

Description

Inverter is connected suppressing method and the system of moment transformer magnetizing current with electrical network

Technical field

The present invention relates to solar photovoltaic technology field, in particular it relates to inverter is connected moment transformation with electrical network The suppressing method of device exciting current and system.

Background technology

Currently, the increasingly evil of the continuous growth with fossil energy consumptions such as oil, coal, natural gass and ball ecological environment Change, a kind of sustainable development and the new forms of energy to ecological environmental nonpollution are all found positive in countries in the world.Solar energy is as one The new forms of energy of kind of efficient pollution-free, it has also become an important ingredient in current energy resource structure.Because solar energy is contained Amount is extremely abundant, and is maked rapid progress using the generation technology of solar energy, therefore solar electrical energy generation obtained both domestic and external extensively Accreditation.Solar grid-connected generating is a kind of effective means using solar energy, and therefore solar grid-connected generating becomes a weight The research topic wanted.In whole electricity generation system, inversion grid connection is an important process, and the conversion to system capacity plays act The effect of sufficient weight.

In inversion grid connection control, great majority are all based on the control of electric current, in this case require first to pass through electrical network Transformator is connected with inverter outlet side, but in the moment being connected electrical network with transformator, if line voltage is applied directly to The vice-side winding of grid-connected transformator, moment can produce very big exciting rush current, such punching in the secondary of grid-connected transformator Hit electric current and can produce larger harm to transformator and electrical network, so the generation of dash current must be suppressed.

The main method of solution static exciter dash current is the method based on hardware soft start at present, as shown in figure 1, Connect a resistance R and a switch S1 in the both sides of grid-connected switch S, allow first before inverter is connected with electrical network and switch S1 Conducting, electrical network passes through resistance R to transformer secondary winding excitation, at the end of transformer secondary winding excitation saturation, connects simultaneously Net switch S, simultaneously roof-cut resistence S1 carry out grid-connected, thus can suppress the generation of static exciter dash current.But this Planting circuit can increase the cost of hardware, and has the consumption of energy on resistance, can affect the efficiency of system.

During realizing the present invention, inventor finds at least there is hardware cost height, energy expenditure in prior art Measure the big and low defect of energy conversion efficiency.

Content of the invention

It is an object of the invention to, for the problems referred to above, propose inverter and be connected moment transformer magnetizing current with electrical network Suppressing method, to realize the advantage that hardware cost is low, energy consumption is little and energy conversion efficiency is high.

The second object of the present invention is, proposes the suppression system that inverter is connected moment transformer magnetizing current with electrical network System.

For achieving the above object, the technical solution used in the present invention is：Inverter is connected moment static exciter with electrical network The suppressing method of electric current, main inclusion：

A, so that inverter is worked, and make output current reference value under synchronous rotating frame for the inverter be all zero；

B, the inverter output voltage of detection conversion to Δ/Y transformer secondary and line voltage；

C, the inverter output voltage of the conversion detecting to Δ/Y transformer secondary is carried out three-phase static coordinate system to Biphase synchronous rotating frame conversion, obtains u_d、u_q；The line voltage detecting is carried out three-phase static coordinate system identical to two Step rotating coordinate system conversion, obtains v_d、v_q；

D, when inverter work make u_d=v_dAnd u_q=v_qWhen, show in grid-connected switch before adhesive, grid-connected switch ends Alternating voltage synchronous, that is, amplitude, frequency and phase place are all identical, and the grid-connected switch of now adhesive will not produce larger transformator Exciting rush current.

Further, before step d, also include transformator is carried out with the operation of excitation in advance.

Further, in stepb, inverter output voltage and the electrical network of Δ/Y transformer secondary is arrived in described detection conversion The operation of voltage, specifically includes：

Obtain inverter output voltage V by voltage sensor senses_ab、V_ca, V_bcBy formula（1）Try to achieve：

V_bc=-(V_ab+V_ca) （1）；

Obtain line voltage v by voltage sensor senses_a、v_c, v_bBy formula（2）Try to achieve：

v_b=-(v_a+v_c) （2）.

Further, in step c, the described inverter output voltage by the conversion detecting to Δ/Y transformer secondary Carry out three-phase static coordinate system to convert to biphase synchronous rotating frame, obtain u_d、u_qOperation, further include：

The line voltage of transformer primary side is converted grid side, the u being obtained by conversion_a、u_b、u_cThrough three phase static coordinate The conversion being tied to biphase synchronous rotating frame obtains u_d、u_q.

Further, the described u line voltage of transformer primary side being converted grid side, being obtained by conversion_a、u_b、u_cThrough The conversion of three-phase static coordinate system to biphase synchronous rotating frame obtains u_d、u_qOperation, specifically include：

Transformator adopts Δ/Y connection it is assumed that turn ratio n=Ns/Np, wherein Ns, Np are respectively transformer secondary, former limit circle Number, n is natural number；By inverter output voltage V_ab、V_ca、V_bcConvert grid side, then there is formula（3）：

Respectively by u_a、u_b、u_cAnd v_a、v_b、v_cAnd i_a、i_b、i_cCarry out being sat to biphase synchronous rotary by three-phase static coordinate system The conversion of mark system obtains formula（4）And formula（5）And formula（6）, wherein, θ is by phaselocked loop：

Work as i_a、i_b、i_cDuring equal to zero, i.e. i_d、i_qIt is also equal to zero, equal according to each point voltage of circuit that electric current is zero, therefore Photovoltaic combining inverter three-phase output voltage u_A、u_B、u_CConvert the voltage of transformer secondary respectively with u_a、u_b、u_cEqual, so Formula（7）It is to set up：

In formula（7）In, wherein, L₂It is the inductance value that filter inductance L converts transformer secondary, ω_gFor electrical network angular frequency Rate； The Δ v that can be obtained through proportional and integral controller by corresponding current error respectively_d、Δv_qGeneration Replace, therefore have formula（8）Set up：

In formula（8）In, k_pFor proportionality coefficient, k_iFor integral coefficient, s is integral operator.

Further, in step d, described inverter work makes u_d=v_dAnd u_q=v_qOperation, specifically include：

Based on formula（8）, make i respectively_d、i_qReference current value i_d*、i_q* it is equal to zero, control photovoltaic combining inverter Output current is zero, then obtain formula（9）Set up：

Now show to convert the voltage u of grid side_aWith v_aFrequency is identical, phase place is identical, voltage magnitude is also identical, u_bWith v_bFrequency is identical, phase place is identical, voltage magnitude is also identical, u_cWith v_cFrequency is identical, phase place is identical, voltage magnitude is also identical；Therefore Each phase voltage of grid-connected switch S both sides is all identical.

Meanwhile, another technical scheme of present invention employing is：Inverter is connected moment transformer magnetizing current with electrical network Suppression system, including the classical three-phase inverting circuit IB being connected successively between photovoltaic array PV and electrical network Grid, three-phase Filter inductance L, Δ/Y connection grid-connected transformator TF and grid-connected switch S, is connected in parallel on described three-phase filter inductance L with Δ/Y connection simultaneously Three-phase filter capacitor C between net transformator TF, and be connected between described three-phase filter inductance L and grid-connected switch S Judgement switch S adhesive algoritic module.

Further, the described work process judging switch S adhesive algoritic module, main inclusion：

A, so that inverter is worked, and make output current reference value under synchronous rotating frame for the inverter be all zero；

B, the inverter output voltage of detection conversion to Δ/Y transformer secondary and line voltage；

C, the inverter output voltage of the conversion detecting to Δ/Y transformer secondary is carried out three-phase static coordinate system to Biphase synchronous rotating frame conversion, obtains u_d、u_q；The line voltage detecting is carried out three-phase static coordinate system identical to two Step rotating coordinate system conversion, obtains v_d、v_q；

D, when inverter work make u_d=v_dAnd u_q=v_qWhen, show in grid-connected switch before adhesive, grid-connected switch ends Alternating voltage synchronous, that is, amplitude, frequency and phase place are all identical, and the grid-connected switch of now adhesive will not produce larger transformator Exciting rush current；

Before step d, also include transformator is carried out with the operation of excitation in advance.

Further, in stepb, inverter output voltage and the electrical network of Δ/Y transformer secondary is arrived in described detection conversion The operation of voltage, specifically includes：

Obtain inverter output voltage V by voltage sensor senses_ab、V_ca, V_bcBy formula（1）Try to achieve：

V_bc=-(V_ab+V_ca) （1）；

Obtain line voltage v by voltage sensor senses_a、v_c, v_bBy formula（2）Try to achieve：

v_b=-(v_a+v_c) （2）.

Further, in step c, the described inverter output voltage by the conversion detecting to Δ/Y transformer secondary Carry out three-phase static coordinate system to convert to biphase synchronous rotating frame, obtain u_d、u_qOperation, specifically include：

Transformator adopts Δ/Y connection it is assumed that turn ratio n=Ns/Np, wherein Ns, Np are respectively transformer secondary, former limit circle Number, n is natural number；By inverter output voltage V_ab、V_ca、V_bcConvert grid side, then there is formula（3）：

Respectively by u_a、u_b、u_cAnd v_a、v_b、v_cAnd i_a、i_b、i_cCarry out being sat to biphase synchronous rotary by three-phase static coordinate system The conversion of mark system obtains formula（4）And formula（5）And formula（6）, wherein, θ is by phaselocked loop：

Work as i_a、i_b、i_cDuring equal to zero, i.e. i_d、i_qIt is also equal to zero, equal according to each point voltage of circuit that electric current is zero, therefore Photovoltaic combining inverter three-phase output voltage u_A、u_B、u_CConvert the voltage of transformer secondary respectively with u_a、u_b、u_cEqual, so Formula（7）It is to set up：

In formula（7）In, wherein, L₂It is the inductance value that filter inductance L converts transformer secondary, ω_gFor electrical network angular frequency Rate； The Δ v that can be obtained through proportional and integral controller by corresponding current error respectively_d、Δv_qGeneration Replace, therefore have formula（8）Set up：

In formula（8）In, k_pFor proportionality coefficient, k_iFor integral coefficient, s is integral operator；

And/or,

In step d, described inverter work makes u_d=v_dAnd u_q=v_qOperation, specifically include：

Based on formula（8）, make i respectively_d、i_qReference current value i_d*、i_q* it is equal to zero, control photovoltaic combining inverter Output current is zero, then obtain formula（9）Set up：

Now show to convert the voltage u of grid side_aWith v_aFrequency is identical, phase place is identical, voltage magnitude is also identical, u_bWith v_bFrequency is identical, phase place is identical, voltage magnitude is also identical, u_cWith v_cFrequency is identical, phase place is identical, voltage magnitude is also identical；Therefore Each phase voltage of grid-connected switch S both sides is all identical.

The inverter of various embodiments of the present invention is connected suppressing method and the system of moment transformer magnetizing current with electrical network, by Mainly include in the method：Make that inverter works and the output current reference value that makes inverter under synchronous rotating frame is all Zero；Inverter output voltage and the line voltage of Δ/Y transformer secondary is arrived in detection conversion；The conversion detecting to Δ/Y is become The inverter output voltage of depressor secondary carries out three-phase static coordinate system and obtains u to the conversion of biphase synchronous rotating frame_d、u_q；Will The line voltage detecting carries out three-phase static coordinate system and obtains v to the conversion of biphase synchronous rotating frame_d、v_q；When inverter work Make u_d=v_dAnd u_q=v_qWhen, show that, in grid-connected switch before adhesive, the alternating voltage of grid-connected switch ends is synchronous；Permissible It is connected moment in inverter with electrical network, judged with software to replace hardware soft starting circuit to suppress transformer magnetizing current, make too The whole process of sun energy photovoltaic generating system can smooth shock-free reliable grid connection；Such that it is able to overcome hardware in prior art The defect that high cost, energy consumption are big and energy conversion efficiency is low, to realize, hardware cost is low, energy consumption is little and energy The advantage of high conversion efficiency.

Other features and advantages of the present invention will illustrate in the following description, and, partly become from description Obtain it is clear that or being understood by implementing the present invention.

Below by drawings and Examples, technical scheme is described in further detail.

Brief description

Accompanying drawing is used for providing a further understanding of the present invention, and constitutes a part for description, the reality with the present invention Apply example and be used for explaining the present invention together, be not construed as limiting the invention.In the accompanying drawings：

The suppression power frequency isolated form photovoltaic combining inverter that Fig. 1 is traditional is connected moment transformer magnetizing current side with electrical network The operation principle schematic diagram of circuit used by method；

The operation principle that Fig. 2 is connected the suppression system of moment transformer magnetizing current for inverter of the present invention with electrical network is illustrated Figure.

In conjunction with accompanying drawing, in the embodiment of the present invention, reference marker is as follows：

PV- photovoltaic array；L- filter inductance；C- filter capacitor；TF- Δ/grid-connected the transformator of Y connection；The grid-connected switch of S-； S1- assists grid-connected switch；R- grid-connected startup resistance；Grid- electrical network；VP- voltage sensor；IP- current sensor；IB- is classical Three-phase inverting circuit；u_A、u_B、u_C- it is respectively photovoltaic combining inverter three-phase output voltage；V_abThe a phase of-transformer primary side and b phase Between line voltage；V_caThe c phase of-transformer primary side and the alternate line voltage of a；u_a、u_b、u_c- respectively primary voltage of transformer converts change Three-phase phase voltage obtained by depressor secondary；v_a、v_b、v_c- three-phase power grid voltage；i_a、i_b、i_c- photovoltaic combining inverter three-phase is defeated Go out phase current.

Specific embodiment

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are illustrated it will be appreciated that preferred reality described herein Apply example to be merely to illustrate and explain the present invention, be not intended to limit the present invention.

The defect existing for prior art, according to embodiments of the present invention, as shown in Figure 2, there is provided inverter and electrical network Connect suppressing method and the system of moment transformer magnetizing current, that is, suppression power frequency isolated form photovoltaic combining inverter and electrical network connect The method connecing moment transformer magnetizing current.This inverter is connected the suppressing method of moment transformer magnetizing current and is with electrical network System, can be connected moment in inverter with electrical network, judge to replace hardware soft starting circuit with software, to suppress static exciter electricity Stream.

The inverter of the present embodiment is connected suppressing method and the system of moment transformer magnetizing current with electrical network, and target is simultaneously , so as to the alternating voltage at two ends is synchronous before adhesive, that is, amplitude, frequency and phase place are all identical for net switch.

Embodiment of the method

The inverter of the present embodiment is connected the suppressing method of moment transformer magnetizing current with electrical network, and main inclusion is following to be walked Suddenly：

So that inverter is worked first, and make its output current reference value under synchronous rotating frame be all zero, then Inverter output voltage and the line voltage of Δ/Y transformer secondary is arrived in detection conversion, by the conversion detecting to Δ/Y transformator The inverter output voltage of secondary carries out three-phase static coordinate system and obtains u to the conversion of biphase synchronous rotating frame_d、u_q, will detect To line voltage carry out three-phase static coordinate system to biphase synchronous rotating frame conversion obtain v_d、v_q.When inverter work makes Obtain u_d=v_dAnd u_q=v_qWhen, show the voltage synchronous of grid-connected switch ends, therefore the grid-connected switch of now adhesive will not produce larger Static exciter dash current.

In the above-described embodiments, obtain inverter output voltage V by voltage sensor senses_ab、V_ca, V_bcBy formula（1） Try to achieve：

V_bc=-(V_ab+V_ca) （1）.

In the above-described embodiments, obtain line voltage v by voltage sensor senses_a、v_c, v_bBy formula（2）Try to achieve：

v_b=-(v_a+v_c) （2）.

In the above-described embodiments, transformator adopts Δ/Y connection it is assumed that turn ratio n=Ns/Np, wherein Ns, Np are respectively transformation Device secondary, the former limit number of turn, by inverter output voltage V_ab、V_ca、V_bcConvert grid side, then there is formula（3）：

In the above-described embodiments, respectively by u_a、u_b、u_cAnd v_a、v_b、v_cAnd i_a、i_b、i_cCarry out by three-phase static coordinate system Conversion to biphase synchronous rotating frame obtains formula（4）And formula（5）And formula（6）, wherein, θ is by phaselocked loop：

In the above-described embodiments, work as i_a、i_b、i_cDuring equal to zero, i.e. i_d、i_qIt is also equal to zero, each according to the circuit that electric current is zero Point voltage is equal, therefore photovoltaic combining inverter three-phase output voltage u_A、u_B、u_CConvert the voltage of transformer secondary respectively with u_a、u_b、u_cEqual, so formula（7）It is to set up.Wherein, L₂It is the inductance value that filter inductance L converts transformer secondary, ω_gFor Electrical network angular frequency.

In formula（7）In, Can respectively by corresponding current error through proportional and integral controller The Δ v obtaining_d、Δv_qReplace, therefore have formula（8）Set up：

In formula（8）In, k_pFor proportionality coefficient, k_iFor integral coefficient, s is integral operator.

Therefore, based on formula（8）, make i respectively_d、i_qReference current value i_d*、i_q* it is equal to zero, control grid-connected inverse Becoming device output current is zero, then can obtain formula（9）Set up：

Now show to convert the voltage u of grid side_aWith v_aFrequency is identical, phase place is identical, voltage magnitude is also identical, u_bWith v_bFrequency is identical, phase place is identical, voltage magnitude is also identical, u_cWith v_cFrequency is identical, phase place is identical, voltage magnitude is also identical, therefore Each phase voltage of grid-connected switch S both sides is all identical, now sends order adhesive grid-connected switch S, due to photovoltaic DC-to-AC converter work Make, excitation has been carried out to transformator in advance, so transformator is not in exciting current shock problem.

System embodiment

The suppression power frequency isolated form photovoltaic combining inverter that Fig. 1 is traditional is connected moment transformer magnetizing current side with electrical network The schematic diagram of method.As shown in figure 1, resistance R and switch S1 series connection, then in parallel with grid-connected switch S.In photovoltaic DC-to-AC converter and electrical network Before connection, switch S1 is allowed to turn on first, electrical network passes through resistance R to transformer secondary winding excitation, through after a while, works as transformation After device vice-side winding excitation terminates, connect grid-connected switch S so that transformer secondary winding connects electrical network, be then cut off switching S1, Complete photovoltaic inverter grid-connected process, by doing so it will the generation of suppression static exciter dash current.But this circuit The cost of hardware can be increased, and the consumption of energy is had on resistance, system effectiveness can be affected.

Fig. 2 is the suppression system that inverter of the present invention is connected moment transformer magnetizing current with electrical network（It is based on three phased The suppression power frequency isolated form photovoltaic combining inverter of system is connected moment transformer magnetizing current system with electrical network）Schematic diagram.

Referring to Fig. 2, the inverter of the present embodiment is connected the suppression system of moment transformer magnetizing current with electrical network, including according to The secondary classical three-phase inverting circuit IB being connected between photovoltaic array PV and electrical network Grid, three-phase filter inductance L, Δ/Y connect Method grid-connected transformator TF and grid-connected switch S, is connected in parallel between described three-phase filter inductance L and Δ/Y connection grid-connected transformator TF Three-phase filter capacitor C, and the judgement switch S adhesive calculation between described three-phase filter inductance L and grid-connected switch S that is connected Method module.

In the above-described embodiments, judge switch S adhesive algoritic module work process, referring in embodiment of the method with regard to inverse Become the related description that device is connected the suppressing method of moment transformer magnetizing current with electrical network, will not be described here.

It follows that the inverter of the above embodiment of the present invention is connected the suppression side of moment transformer magnetizing current with electrical network Method and system, three-phase power grid voltage is obtained v through the conversion of three-phase static coordinate system to biphase synchronous rotating frame_d、v_q. The line voltage of transformer primary side is converted grid side, the u being obtained by conversion_a、u_b、u_cThrough three-phase static coordinate system to biphase The conversion of synchronous rotating frame obtains u_d、u_q.By controlling photovoltaic DC-to-AC converter output current to be zero so that final u_d、u_qRespectively Equal to v_d、v_q, thus reaching, inverter output voltage is synchronous with line voltage, thus adhesive grid-connected switch S, transformator would not Produce exciting rush current.This inverter is connected suppressing method and the system of moment transformer magnetizing current with electrical network, not only fits For three-phase photovoltaic grid-connected electricity generation system, it is also applied for single-phase grid-connected photovoltaic power generation system, have a good application prospect and city Field is worth.

In sum, the inverter of the various embodiments described above of the present invention is connected the suppression of moment transformer magnetizing current with electrical network Method and system, can suppress the dash current of static exciter well, and does not need to increase extra hardware soft start electricity Road is so that the whole process of solar photovoltaic generation system can smooth shock-free reliable grid connection；Have hardware cost low, effect Rate is high, reliability is high, control simple advantage.

Finally it should be noted that：The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, Although being described in detail to the present invention with reference to the foregoing embodiments, for a person skilled in the art, it still may be used To modify to the technical scheme described in foregoing embodiments, or equivalent is carried out to wherein some technical characteristics. All any modification, equivalent substitution and improvement within the spirit and principles in the present invention, made etc., should be included in the present invention's Within protection domain.

Claims (4)

1. inverter is connected the suppressing method of moment transformer magnetizing current it is characterised in that main include with electrical network：

A, so that inverter is worked, and make output current reference value under synchronous rotating frame for the inverter be all zero；

B, the inverter output voltage of detection conversion to Δ/Y transformer secondary and line voltage；

C, the inverter output voltage of the conversion detecting to Δ/Y transformer secondary is carried out three-phase static coordinate system to biphase Synchronous rotating frame converts, and obtains u_d、u_q；The line voltage detecting is carried out three-phase static coordinate system revolve to two synchronised Turn coordinate system transformation, obtain v_d、v_q；

D, when inverter work make u_d=v_dAnd u_q=v_qWhen, show in grid-connected switch before adhesive, grid-connected switch ends Alternating voltage is synchronous, and that is, amplitude, frequency and phase place are all identical, and the grid-connected switch of now adhesive will not produce larger transformator and encourage Magnetic dash current；

In stepb, Δ/inverter output voltage of Y transformer secondary and the operation of line voltage, tool are arrived in described detection conversion Body includes：

Obtain inverter output voltage V by voltage sensor senses_ab、V_ca, V_bcTried to achieve by formula (1)：

V_bc=-(V_ab+V_ca) (1)；

Obtain line voltage v by voltage sensor senses_a、v_c, v_bTried to achieve by formula (2)：

v_b=-(v_a+v_c) (2)；

In step c, the described inverter output voltage by the conversion detecting to Δ/Y transformer secondary carries out three phase static Coordinate system converts to biphase synchronous rotating frame, obtains u_d、u_qOperation, further include：

The line voltage of transformer primary side is converted grid side, the u being obtained by conversion_a、u_b、u_cArrive through three-phase static coordinate system The conversion of biphase synchronous rotating frame obtains u_d、u_q；

In step d, described inverter work makes u_d=v_dAnd u_q=v_qOperation, specifically include：

Based on formula (8),

$\left\{\begin{array}{c}{u}_d={\mathrm{\Δv}}_d-{\mathrm{\ω}}_g{L}_2{i}_q+v_d=(i_d^{*}-i_d)\·(k_p+k_i/s)-{\mathrm{\ω}}_g{L}_2{i}_q+v_d\\ u_q={\mathrm{\Δv}}_q+{\mathrm{\ω}}_g{L}_2{i}_d+v_q=(i_q^{*}-i_q)\·(k_p+k_i/s)+{\mathrm{\ω}}_g{L}_2{i}_d+v_q\end{array}\right.---\left(8\right)$

The △ v that can be obtained through proportional and integral controller by corresponding current error respectively_d、△v_qGeneration Replace, L₂It is the inductance value that filter inductance L converts transformer secondary, ω_gFor electrical network angular frequency, k_pFor proportionality coefficient, k_iFor integration Coefficient, s is integral operator；The inverter output current of the conversion detecting to Δ/Y transformer secondary is carried out three phase static seat Mark system, to the conversion of biphase synchronous rotating frame, obtains i_d、i_q, make i respectively_d、i_qReference current valueIt is equal to zero, control Photovoltaic grid connection inverter output current processed is zero, then obtain formula (9) and set up：

$\left\{\begin{array}{c}{u}_d=v_d\\ u_q=v_q\end{array}\right.---\left(9\right);$

Now show to convert the voltage u of grid side_aWith v_aFrequency is identical, phase place is identical, voltage magnitude is also identical, u_bWith v_bFrequency Identical, phase place is identical, voltage magnitude is also identical, u_cWith v_cFrequency is identical, phase place is identical, voltage magnitude is also identical；Therefore grid-connected open The each phase voltage closing S both sides is all identical.

2. inverter according to claim 1 is connected the suppressing method of moment transformer magnetizing current, its feature with electrical network It is, before step d, also include transformator is carried out with the operation of excitation in advance.

3. inverter according to claim 1 is connected the suppressing method of moment transformer magnetizing current, its feature with electrical network It is, the described u line voltage of transformer primary side being converted grid side, being obtained by conversion_a、u_b、u_cThrough three phase static coordinate The conversion being tied to biphase synchronous rotating frame obtains u_d、u_qOperation, specifically include：

Transformator adopts Δ/Y connection it is assumed that turn ratio n=Ns/Np, wherein Ns, Np are respectively transformer secondary, the former limit number of turn, n For natural number；By inverter output voltage V_ab、V_ca、V_bcConvert grid side, then there is formula (3)：

$\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]=\left[\begin{array}{c}n{V}_{ab}\\ {\mathrm{nV}}_{bc}\\ {\mathrm{nV}}_{ca}\end{array}\right]---\left(3\right);$

Respectively by u_a、u_b、u_cAnd v_a、v_b、v_cAnd i_a、i_b、i_cCarry out by three-phase static coordinate system to biphase synchronous rotating frame Conversion obtain formula (4) and formula (5) and formula (6), wherein, θ is by phaselocked loop：

$\left[\begin{array}{c}{u}_d\\ u_q\end{array}\right]=\frac{2}{3}\·\left[\begin{array}{ccc}cos\mathrm{\θ}& cos(\mathrm{\θ}-\frac{2}{3}\mathrm{\π})& cos(\mathrm{\θ}+\frac{2}{3}\mathrm{\π})\\ sin\mathrm{\θ}& sin(\mathrm{\θ}-\frac{2}{3}\mathrm{\π})& sin(\mathrm{\θ}+\frac{2}{3}\mathrm{\π})\end{array}\right]\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]---\left(4\right);$

$\left[\begin{array}{c}{v}_d\\ v_q\end{array}\right]=\frac{2}{3}\·\left[\begin{array}{ccc}cos\mathrm{\θ}& cos(\mathrm{\θ}-\frac{2}{3}\mathrm{\π})& cos(\mathrm{\θ}+\frac{2}{3}\mathrm{\π})\\ sin\mathrm{\θ}& sin(\mathrm{\θ}-\frac{2}{3}\mathrm{\π})& sin(\mathrm{\θ}+\frac{2}{3}\mathrm{\π})\end{array}\right]\left[\begin{array}{c}{v}_a\\ v_b\\ v_c\end{array}\right]---\left(5\right);$

$\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]=\frac{2}{3}\·\left[\begin{array}{ccc}\cos \mathrm{\θ}& \cos (\mathrm{\θ}-\frac{2}{3}\mathrm{\π})& \cos (\mathrm{\θ}+\frac{2}{3}\mathrm{\π})\\ \sin \mathrm{\θ}& \sin (\mathrm{\θ}-\frac{2}{3}\mathrm{\π})& \sin (\mathrm{\θ}+\frac{2}{3}\mathrm{\π})\end{array}\right]\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]---\left(6\right);$

Work as i_a、i_b、i_cDuring equal to zero, i.e. i_d、i_qIt is also equal to zero, therefore photovoltaic equal according to each point voltage of circuit that electric current is zero Combining inverter three-phase output voltage u_A、u_B、u_CConvert the voltage of transformer secondary respectively with u_a、u_b、u_cEqual, so formula (7) it is to set up：

$\left\{\begin{array}{c}{u}_d=L_2\frac{{\mathrm{di}}_d}{dt}-{\mathrm{\ω}}_g{L}_2{i}_q+v_d\\ u_q=L_2\frac{{\mathrm{di}}_q}{dt}+{\mathrm{\ω}}_g{L}_2{i}_d+v_q\end{array}\right.---\left(7\right);$

In formula (7), wherein, L₂It is the inductance value that filter inductance L converts transformer secondary, ω_gFor electrical network angular frequency；The △ v that can be obtained through proportional and integral controller by corresponding current error respectively_d、△v_qReplace, Formula (8) is therefore had to set up：

$\left\{\begin{array}{c}{u}_d={\mathrm{\Δv}}_d-{\mathrm{\ω}}_g{L}_2{i}_q+v_d=(i_d^{*}-i_d)\·(k_p+k_i/s)-{\mathrm{\ω}}_g{L}_2{i}_q+v_d\\ u_q={\mathrm{\Δv}}_q+{\mathrm{\ω}}_g{L}_2{i}_d+v_q=(i_q^{*}-i_q)\·(k_p+k_i/s)+{\mathrm{\ω}}_g{L}_2{i}_d+v_q\end{array}\right.---\left(8\right);$

In formula (8), k_pFor proportionality coefficient, k_iFor integral coefficient, s is integral operator.

4. inverter is connected the suppression system of moment transformer magnetizing current it is characterised in that including cooperation successively even with electrical network It is connected on three-phase inverting circuit IB between photovoltaic array PV and electrical network Grid, three-phase filter inductance L, the Δ/grid-connected transformator of Y connection TF and grid-connected switch S, is connected in parallel on the three-phase filter capacitor between described three-phase filter inductance L and Δ/Y connection grid-connected transformator TF C, and the judgement switch S adhesive algoritic module between described three-phase filter inductance L and grid-connected switch S that is connected；

The described work process judging switch S adhesive algoritic module, main inclusion：

A, so that inverter is worked, and make output current reference value under synchronous rotating frame for the inverter be all zero；

B, the inverter output voltage of detection conversion to Δ/Y transformer secondary and line voltage；

C, the inverter output voltage of the conversion detecting to Δ/Y transformer secondary is carried out three-phase static coordinate system to biphase Synchronous rotating frame converts, and obtains u_d、u_q；The line voltage detecting is carried out three-phase static coordinate system revolve to two synchronised Turn coordinate system transformation, obtain v_d、v_q；

D, when inverter work make u_d=v_dAnd u_q=v_qWhen, show in grid-connected switch before adhesive, grid-connected switch ends Alternating voltage is synchronous, and that is, amplitude, frequency and phase place are all identical, and the grid-connected switch of now adhesive will not produce larger transformator and encourage Magnetic dash current；

Before step d, also include transformator is carried out with the operation of excitation in advance；

In stepb, Δ/inverter output voltage of Y transformer secondary and the operation of line voltage, tool are arrived in described detection conversion Body includes：

Obtain inverter output voltage V by voltage sensor senses_ab、V_ca, V_bcTried to achieve by formula (1)：

V_bc=-(V_ab+V_ca) (1)；

Obtain line voltage v by voltage sensor senses_a、v_c, v_bTried to achieve by formula (2)：

v_b=-(v_a+v_c) (2)；

In step c, the described inverter output voltage by the conversion detecting to Δ/Y transformer secondary carries out three phase static Coordinate system converts to biphase synchronous rotating frame, obtains u_d、u_qOperation, specifically include：

Transformator adopts Δ/Y connection it is assumed that turn ratio n=Ns/Np, wherein Ns, Np are respectively transformer secondary, the former limit number of turn, n For natural number；By inverter output voltage V_ab、V_ca、V_bcConvert grid side, then there is formula (3)：

$\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]=\left[\begin{array}{c}n{V}_{ab}\\ {\mathrm{nV}}_{bc}\\ {\mathrm{nV}}_{ca}\end{array}\right]---\left(3\right);$

Respectively by u_a、u_b、u_cAnd v_a、v_b、v_cAnd i_a、i_b、i_cCarry out by three-phase static coordinate system to biphase synchronous rotating frame Conversion obtain formula (4) and formula (5) and formula (6), wherein, θ is by phaselocked loop：

$\left[\begin{array}{c}{u}_d\\ u_q\end{array}\right]=\frac{2}{3}\·\left[\begin{array}{ccc}cos\mathrm{\θ}& cos(\mathrm{\θ}-\frac{2}{3}\mathrm{\π})& cos(\mathrm{\θ}+\frac{2}{3}\mathrm{\π})\\ sin\mathrm{\θ}& sin(\mathrm{\θ}-\frac{2}{3}\mathrm{\π})& sin(\mathrm{\θ}+\frac{2}{3}\mathrm{\π})\end{array}\right]\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]---\left(4\right);$

$\left[\begin{array}{c}{v}_d\\ v_q\end{array}\right]=\frac{2}{3}\·\left[\begin{array}{ccc}cos\mathrm{\θ}& cos(\mathrm{\θ}-\frac{2}{3}\mathrm{\π})& cos(\mathrm{\θ}+\frac{2}{3}\mathrm{\π})\\ sin\mathrm{\θ}& sin(\mathrm{\θ}-\frac{2}{3}\mathrm{\π})& sin(\mathrm{\θ}+\frac{2}{3}\mathrm{\π})\end{array}\right]\left[\begin{array}{c}{v}_a\\ v_b\\ v_c\end{array}\right]---\left(5\right);$

$\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]=\frac{2}{3}\·\left[\begin{array}{ccc}\cos \mathrm{\θ}& \cos (\mathrm{\θ}-\frac{2}{3}\mathrm{\π})& \cos (\mathrm{\θ}+\frac{2}{3}\mathrm{\π})\\ \sin \mathrm{\θ}& \sin (\mathrm{\θ}-\frac{2}{3}\mathrm{\π})& \sin (\mathrm{\θ}+\frac{2}{3}\mathrm{\π})\end{array}\right]\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]---\left(6\right);$

Work as i_a、i_b、i_cDuring equal to zero, i.e. i_d、i_qIt is also equal to zero, therefore photovoltaic equal according to each point voltage of circuit that electric current is zero Combining inverter three-phase output voltage u_A、u_B、u_CConvert the voltage of transformer secondary respectively with u_a、u_b、u_cEqual, so formula (7) it is to set up：

$\left\{\begin{array}{c}{u}_d=L_2\frac{{\mathrm{di}}_d}{dt}-{\mathrm{\ω}}_g{L}_2{i}_q+v_d\\ u_q=L_2\frac{{\mathrm{di}}_q}{dt}+{\mathrm{\ω}}_g{L}_2{i}_d+v_q\end{array}\right.---\left(7\right);$

In formula (7), wherein, L₂It is the inductance value that filter inductance L converts transformer secondary, ω_gFor electrical network angular frequency；The △ v that can be obtained through proportional and integral controller by corresponding current error respectively_d、△v_qReplace, Formula (8) is therefore had to set up：

$\left\{\begin{array}{c}{u}_d={\mathrm{\Δv}}_d-{\mathrm{\ω}}_g{L}_2{i}_q+v_d=(i_d^{*}-i_d)\·(k_p+k_i/s)-{\mathrm{\ω}}_g{L}_2{i}_q+v_d\\ u_q={\mathrm{\Δv}}_q+{\mathrm{\ω}}_g{L}_2{i}_d+v_q=(i_q^{*}-i_q)\·(k_p+k_i/s)+{\mathrm{\ω}}_g{L}_2{i}_d+v_q\end{array}\right.---\left(8\right);$

In formula (8), k_pFor proportionality coefficient, k_iFor integral coefficient, s is integral operator；

And/or,

In step d, described inverter work makes u_d=v_dAnd u_q=v_qOperation, specifically include：

Based on formula (8), make i respectively_d、i_qReference current valueIt is equal to zero, control photovoltaic combining inverter output electricity Stream is zero, then obtain formula (9) and set up：

$\left\{\begin{array}{c}{u}_d=v_d\\ u_q=v_q\end{array}\right.---\left(9\right);$

Now show to convert the voltage u of grid side_aWith v_aFrequency is identical, phase place is identical, voltage magnitude is also identical, u_bWith v_bFrequency Identical, phase place is identical, voltage magnitude is also identical, u_cWith v_cFrequency is identical, phase place is identical, voltage magnitude is also identical；Therefore grid-connected open The each phase voltage closing S both sides is all identical.