CN103812134A - 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 the inhibition method and system of moment transformer magnetizing current with electrical network

Technical field

The present invention relates to solar photovoltaic technology field, particularly, relate to inverter is connected moment transformer magnetizing current inhibition method and system with electrical network.

Background technology

Current, along with the continuous growth of fossil energy consumption and going from bad to worse of ball ecological environment such as oil, coal, natural gases, countries in the world are all in a kind of sustainable development of positive searching and to the free of contamination new forms of energy of biological environment.Solar energy, as a kind of new forms of energy of efficient pollution-free, has become an important part in current energy resource structure.Because solar energy reserves are extremely abundant, and utilize the generation technology of solar energy to make rapid progress, therefore solar power generation has obtained extensive approval both domestic and external.Solar grid-connected generating is a kind of effective means of utilizing solar energy, and therefore solar grid-connected generating becomes an important research topic.In whole electricity generation system, inversion grid connection is an important process, plays a part very important to the conversion of system capacity.

In inversion grid connection control, great majority are all the control based on electric current, require in this case first electrical network to be connected with inverter outlet side by transformer, but in the moment that electrical network is connected with transformer, if line voltage is directly added to the secondary winding of grid-connected transformer, moment can produce very large exciting rush current at the secondary of grid-connected transformer, and such impulse current can produce larger harm to transformer and electrical network, so must suppress the generation of impulse current.

The main method that solves at present static exciter impulse current is the method based on hardware soft start, as shown in Figure 1, connect a resistance R and a switch S 1 in the both sides of grid-connected switch S, before being connected with electrical network, inverter first allows switch S1 conducting, electrical network to transformer secondary winding excitation, in the time of the saturated end of transformer secondary winding excitation, is connected grid-connected switch S by resistance R, cut off switch S 1 simultaneously and carry out grid-connectedly, so just can suppress the generation of static exciter impulse current.But sort circuit can increase the cost of hardware, and on resistance, have the consumption of energy, can affect the efficiency of system.

Realizing in process of the present invention, inventor finds at least to exist in prior art the defect such as hardware cost is high, energy consumption is large and energy conversion efficiency is low.

Summary of the invention

The object of the invention is to, for the problems referred to above, propose inverter is connected moment transformer magnetizing current inhibition method with electrical network, 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 inverter is connected moment transformer magnetizing current inhibition system with electrical network.

For achieving the above object, the technical solution used in the present invention is: inverter is connected the inhibition method of moment transformer magnetizing current with electrical network, mainly comprise:

A, make inverter work, and to make the output current reference value of inverter under synchronous rotating frame be all zero;

Inverter output voltage and the line voltage of Δ/Y transformer secondary arrived in b, detection conversion;

C, the conversion detecting is carried out to three phase static coordinate system to two-phase synchronous rotating frame conversion to the inverter output voltage of Δ/Y transformer secondary, obtain u _d, u _q; The line voltage detecting is carried out to three phase static coordinate system to the conversion of two-phase synchronous rotating frame, obtain v _d, v _q;

D, make u when inverter work _d=v _dand u _q=v _qtime, show that at grid-connected switch the alternating voltage of grid-connected switch ends is synchronous before adhesive, amplitude, frequency and phase place are all identical, and the grid-connected switch of now adhesive can not produce larger static exciter impulse current.

Further, before steps d, also comprise transformer is carried out to the operation of excitation in advance.

Further, in step b, the inverter output voltage of Δ/Y transformer secondary and the operation of line voltage are converted in described detection, specifically comprise:

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）。

Further, in step c, described the conversion detecting is carried out to three phase static coordinate system to two-phase synchronous rotating frame conversion to the inverter output voltage of Δ/Y transformer secondary, obtain u _d, u _qoperation, further comprise:

The line voltage of transformer primary side is converted to grid side, the u being obtained by conversion _a, u _b, u _cthe conversion that is tied to two-phase synchronous rotating frame through three phase static coordinate obtains u _d, u _q.

Further, the described line voltage by transformer primary side is converted grid side, the u being obtained by conversion _a, u _b, u _cthe conversion that is tied to two-phase synchronous rotating frame through three phase static coordinate obtains u _d, u _qoperation, specifically comprise:

Transformer adopting Δ/Y connection, supposes turn ratio n=Ns/Np, and wherein Ns, Np are respectively transformer secondary, the former limit number of turn, and n is natural number; By inverter output voltage V _ab, V _ca, V _bcto grid side, there is formula (3) in conversion:

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

Respectively by u _a, u _b, u _cand v _a, v _b, v _cand i _a, i _b, i _cthe conversion of carrying out being tied to by three phase static coordinate two-phase synchronous rotating frame obtains formula (4) and formula (5) and formula (6), and wherein, θ is by phase-locked loop:

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

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

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

Work as i _a, i _b, i _cwhile equalling zero, i.e. i _d, i _qalso equal zero, the each point voltage of circuit that is zero according to electric current equates, therefore photovoltaic combining inverter three-phase output voltage u _a, u _b, u _cconversion to the voltage of transformer secondary respectively with u _a, u _b, u _cequate, so formula (7) is set up:

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

In formula (7), wherein, L ₂the inductance value that filter inductance L converts transformer secondary, ω _gfor electrical network angular frequency;

the Δ v that can be obtained through proportional and integral controller by corresponding current error respectively _d, Δ v _qreplace, therefore have formula (8) to set up:

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

In formula (8), k _pfor proportionality coefficient, k _ifor integral coefficient, s is integral operator.

Further, in steps d, described inverter work makes u _d=v _dand u _q=v _qoperation, specifically comprise:

Based on formula (8), make respectively i _d, i _qreference current value i _d*, i _q* all equal zero, controlling photovoltaic grid connection inverter output current is zero, obtains formula (9) and sets up:

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

Now show the voltage u of conversion to 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.

Simultaneously, another technical scheme that the present invention adopts is: inverter is connected the inhibition system of moment transformer magnetizing current with electrical network, comprise classical three-phase inverting circuit IB, the three-phase filter inductance L, the grid-connected transformer TF of Δ/Y connection and the grid-connected switch S that are connected successively between photovoltaic array PV and electrical network Grid, be connected in parallel on the three-phase filter capacitor C between the grid-connected transformer TF of described three-phase filter inductance L and Δ/Y connection, and the judgement switch S adhesive algoritic module being connected between described three-phase filter inductance L and grid-connected switch S.

Further, the course of work of described judgement switch S adhesive algoritic module, mainly comprises:

A, make inverter work, and to make the output current reference value of inverter under synchronous rotating frame be all zero;

Inverter output voltage and the line voltage of Δ/Y transformer secondary arrived in b, detection conversion;

C, the conversion detecting is carried out to three phase static coordinate system to two-phase synchronous rotating frame conversion to the inverter output voltage of Δ/Y transformer secondary, obtain u _d, u _q; The line voltage detecting is carried out to three phase static coordinate system to the conversion of two-phase synchronous rotating frame, obtain v _d, v _q;

D, make u when inverter work _d=v _dand u _q=v _qtime, show that at grid-connected switch the alternating voltage of grid-connected switch ends is synchronous before adhesive, amplitude, frequency and phase place are all identical, and the grid-connected switch of now adhesive can not produce larger static exciter impulse current;

Before steps d, also comprise transformer is carried out to the operation of excitation in advance.

Further, in step b, the inverter output voltage of Δ/Y transformer secondary and the operation of line voltage are converted in described detection, specifically comprise:

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）。

Further, in step c, described the conversion detecting is carried out to three phase static coordinate system to two-phase synchronous rotating frame conversion to the inverter output voltage of Δ/Y transformer secondary, obtain u _d, u _qoperation, specifically comprise:

Transformer adopting Δ/Y connection, supposes turn ratio n=Ns/Np, and wherein Ns, Np are respectively transformer secondary, the former limit number of turn, and n is natural number; By inverter output voltage V _ab, V _ca, V _bcto grid side, there is formula (3) in conversion:

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

Respectively by u _a, u _b, u _cand v _a, v _b, v _cand i _a, i _b, i _cthe conversion of carrying out being tied to by three phase static coordinate two-phase synchronous rotating frame obtains formula (4) and formula (5) and formula (6), and wherein, θ is by phase-locked loop:

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

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

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

Work as i _a, i _b, i _cwhile equalling zero, i.e. i _d, i _qalso equal zero, the each point voltage of circuit that is zero according to electric current equates, therefore photovoltaic combining inverter three-phase output voltage u _a, u _b, u _cconversion to the voltage of transformer secondary respectively with u _a, u _b, u _cequate, so formula (7) is set up:

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

In formula (7), wherein, L ₂the inductance value that filter inductance L converts transformer secondary, ω _gfor electrical network angular frequency;

the Δ v that can be obtained through proportional and integral controller by corresponding current error respectively _d, Δ v _qreplace, therefore have formula (8) to set up:

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

In formula (8), k _pfor proportionality coefficient, k _ifor integral coefficient, s is integral operator;

And/or,

In steps d, described inverter work makes u _d=v _dand u _q=v _qoperation, specifically comprise:

Based on formula (8), make respectively i _d, i _qreference current value i _d*, i _q* all equal zero, controlling photovoltaic grid connection inverter output current is zero, obtains formula (9) and sets up:

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

Now show the voltage u of conversion to 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 the inhibition method and system of moment transformer magnetizing current with electrical network, because the method mainly comprises: making inverter work and making the output current reference value of inverter under synchronous rotating frame is all zero; Detect inverter output voltage and the line voltage of conversion to Δ/Y transformer secondary; The conversion detecting is carried out to three phase static coordinate system to the inverter output voltage of Δ/Y transformer secondary and obtain u to the conversion of two-phase synchronous rotating frame _d, u _q; The line voltage detecting is carried out to three phase static coordinate system and obtain v to the conversion of two-phase synchronous rotating frame _d, v _q; When inverter work makes u _d=v _dand u _q=v _qtime, show that at grid-connected switch the alternating voltage of grid-connected switch ends is synchronous before adhesive; Can be connected moment with electrical network at inverter, judge and replace hardware soft starting circuit to suppress transformer magnetizing current with software, make the whole process of solar photovoltaic generation system can be smoothly shock-free reliably grid-connected; Thereby can overcome the defect that in prior art, hardware cost is high, energy consumption is large and energy conversion efficiency is low, to realize the advantage that hardware cost is low, energy consumption is little and energy conversion efficiency is high.

Other features and advantages of the present invention will be set forth in the following description, and, partly from specification, become apparent, or understand by implementing the present invention.

Below by drawings and Examples, technical scheme of the present invention is described in further detail.

Accompanying drawing explanation

Accompanying drawing is used to provide a further understanding of the present invention, and forms a part for specification, for explaining the present invention, is not construed as limiting the invention together with embodiments of the present invention.In the accompanying drawings:

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

Fig. 2 is inverter of the present invention is connected the inhibition system of moment transformer magnetizing current operation principle schematic diagram with electrical network.

By reference to the accompanying drawings, in the embodiment of the present invention, reference marker is as follows:

PV-photovoltaic array; L-filter inductance; C-filter capacitor; The grid-connected transformer of TF-Δ/Y connection; The grid-connected switch of S-; S1-assists grid-connected switch; The grid-connected starting resistance of R-; Grid-electrical network; VP-voltage sensor; IP-current sensor; The classical three-phase inverting circuit of IB-; u _a, u _b, u _c-be respectively photovoltaic combining inverter three-phase output voltage; V _abthe a phase of-transformer primary side and b phase top-stitching voltage; V _cathe c phase of-transformer primary side and a phase top-stitching voltage; u _a, u _b, u _c-be respectively transformer primary polygonal voltage to convert the three-phase phase voltage that transformer secondary obtains; v _a, v _b, v _c-three phase network voltage; i _a, i _b, i _c-photovoltaic combining inverter three-phase output current phase.

Embodiment

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described, should be appreciated that preferred embodiment described herein, only for description and interpretation the present invention, is not intended to limit the present invention.

The defect existing for prior art, according to the embodiment of the present invention, as shown in Figure 2, provide inverter to be connected the inhibition method and system of moment transformer magnetizing current with electrical network, suppressed power frequency isolated form photovoltaic combining inverter is connected moment transformer magnetizing current method with electrical network.This inverter is connected the inhibition method and system of moment transformer magnetizing current with electrical network, can be connected moment with electrical network at inverter, judges and replaces hardware soft starting circuit with software, suppresses transformer magnetizing current.

The inverter of the present embodiment is connected the inhibition method and system of moment transformer magnetizing current with electrical network, target be grid-connected switch before adhesive, make the alternating voltage at its two ends synchronous, amplitude, frequency and phase place are all identical.

embodiment of the method

The inverter of the present embodiment is connected the inhibition method of moment transformer magnetizing current with electrical network, mainly comprise the following steps:

First make inverter work, and making its output current reference value under synchronous rotating frame is all zero, then detect inverter output voltage and the line voltage of conversion to Δ/Y transformer secondary, the conversion detecting is carried out to three phase static coordinate system to the inverter output voltage of Δ/Y transformer secondary and obtain u to the conversion of two-phase synchronous rotating frame _d, u _q, the line voltage detecting is carried out to three phase static coordinate system and obtains v to the conversion of two-phase synchronous rotating frame _d, v _q.When inverter work makes u _d=v _dand u _q=v _qtime, show that the voltage of grid-connected switch ends is synchronous, therefore the grid-connected switch of now adhesive can not produce larger static exciter impulse current.

In the above-described embodiments, 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）。

In the above-described embodiments, 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 the above-described embodiments, transformer adopting Δ/Y connection, supposes turn ratio n=Ns/Np, and wherein Ns, Np are respectively transformer secondary, the former limit number of turn, by inverter output voltage V _ab, V _ca, V _bcto grid side, there is formula (3) in conversion:

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

In the above-described embodiments, respectively by u _a, u _b, u _cand v _a, v _b, v _cand i _a, i _b, i _cthe conversion of carrying out being tied to by three phase static coordinate two-phase synchronous rotating frame obtains formula (4) and formula (5) and formula (6), and wherein, θ is by phase-locked loop:

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

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

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

In the above-described embodiments, work as i _a, i _b, i _cwhile equalling zero, i.e. i _d, i _qalso equal zero, the each point voltage of circuit that is zero according to electric current equates, therefore photovoltaic combining inverter three-phase output voltage u _a, u _b, u _cconversion to the voltage of transformer secondary respectively with u _a, u _b, u _cequate, so formula (7) is set up.Wherein, L ₂the inductance value that filter inductance L converts transformer secondary, ω _gfor electrical network angular frequency.

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

In formula (7),

the Δ v that can be obtained through proportional and integral controller by corresponding current error respectively _d, Δ v _qreplace, therefore have formula (8) to set up:

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

In formula (8), k _pfor proportionality coefficient, k _ifor integral coefficient, s is integral operator.

Therefore,, based on formula (8), make respectively i _d, i _qreference current value i _d*, i _q* all equal zero, controlling photovoltaic grid connection inverter output current is zero, can 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 the voltage u of conversion to 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, and the grid-connected switch S of adhesive of now giving an order, because photovoltaic DC-to-AC converter is worked, transformer transformer carried out to excitation in advance, so can not exist exciting current shock problem.

system embodiment

Fig. 1 is traditional inhibition power frequency isolated form photovoltaic combining inverter is connected moment transformer magnetizing current method schematic diagram with electrical network.As shown in Figure 1, resistance R and switch S 1 are connected, then in parallel with grid-connected switch S.Before photovoltaic DC-to-AC converter is connected with electrical network, first allow switch S1 conducting, electrical network by resistance R to transformer secondary winding excitation, through after a while, after transformer secondary winding excitation finishes, connect grid-connected switch S, make transformer secondary winding connect electrical network, then cut off switch S 1, complete photovoltaic inverter grid-connected process, do like this generation that just can suppress static exciter impulse current.But sort circuit can increase the cost of hardware, and on resistance, have the consumption of energy, can affect system effectiveness.

Fig. 2 is inverter of the present invention is connected moment transformer magnetizing current inhibition system (being connected moment transformer magnetizing current system with electrical network based on three facies-controlled inhibition power frequency isolated form photovoltaic combining inverters) schematic diagram with electrical network.

Referring to Fig. 2, the inverter of the present embodiment is connected the inhibition system of moment transformer magnetizing current with electrical network, comprise classical three-phase inverting circuit IB, the three-phase filter inductance L, the grid-connected transformer TF of Δ/Y connection and the grid-connected switch S that are connected successively between photovoltaic array PV and electrical network Grid, be connected in parallel on the three-phase filter capacitor C between the grid-connected transformer TF of described three-phase filter inductance L and Δ/Y connection, and the judgement switch S adhesive algoritic module being connected between described three-phase filter inductance L and grid-connected switch S.

In the above-described embodiments, judge the course of work of switch S adhesive algoritic module, referring to the related description that is connected the inhibition method of moment transformer magnetizing current in embodiment of the method about inverter with electrical network, do not repeat them here.

Hence one can see that, and the inverter of the above embodiment of the present invention is connected the inhibition method and system of moment transformer magnetizing current with electrical network, and the conversion that three phase network voltage is tied to two-phase synchronous rotating frame through three phase static coordinate obtains v _d, v _q.The line voltage of transformer primary side is converted to grid side, the u being obtained by conversion _a, u _b, u _cthe conversion that is tied to two-phase synchronous rotating frame through three phase static coordinate obtains u _d, u _q.Be zero by controlling photovoltaic DC-to-AC converter output current, make final u _d, u _qequal respectively v _d, v _qthereby, reach inverter output voltage and synchronize with line voltage, thus the grid-connected switch S of adhesive, and transformer just can not produce exciting rush current.This inverter is connected the inhibition method and system of moment transformer magnetizing current with electrical network, be not only applicable to three-phase photovoltaic grid-connected electricity generation system, is also applicable to single-phase grid-connected photovoltaic power generation system, has a good application prospect and market value.

In sum, the inverter of the various embodiments described above of the present invention is connected the inhibition method and system of moment transformer magnetizing current with electrical network, can suppress well the impulse current of static exciter, and not needing increases extra hardware soft starting circuit, make the whole process of solar photovoltaic generation system can be smoothly shock-free reliably grid-connected; Have that hardware cost is low, efficiency 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 the present invention is had been described in detail with reference to previous embodiment, for a person skilled in the art, its technical scheme that still can record aforementioned each embodiment is modified, or part technical characterictic is wherein equal to replacement.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.

Claims (4)

1. inverter is connected the inhibition method of moment transformer magnetizing current with electrical network, it is characterized in that, mainly comprises:

A, make inverter work, and to make the output current reference value of inverter under synchronous rotating frame be all zero;

Inverter output voltage and the line voltage of Δ/Y transformer secondary arrived in b, detection conversion;

C, the conversion detecting is carried out to three phase static coordinate system to two-phase synchronous rotating frame conversion to the inverter output voltage of Δ/Y transformer secondary, obtain u _d, u _q; The line voltage detecting is carried out to three phase static coordinate system to the conversion of two-phase synchronous rotating frame, obtain v _d, v _q;

D, make u when inverter work _d=v _dand u _q=v _qtime, show that at grid-connected switch the alternating voltage of grid-connected switch ends is synchronous before adhesive, amplitude, frequency and phase place are all identical, and the grid-connected switch of now adhesive can not produce larger static exciter impulse current;

In step b, the inverter output voltage of Δ/Y transformer secondary and the operation of line voltage are converted in described detection, specifically comprise:

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, described the conversion detecting is carried out to three phase static coordinate system to two-phase synchronous rotating frame conversion to the inverter output voltage of Δ/Y transformer secondary, obtain u _d, u _qoperation, further comprise:

The line voltage of transformer primary side is converted to grid side, the u being obtained by conversion _a, u _b, u _cthe conversion that is tied to two-phase synchronous rotating frame through three phase static coordinate obtains u _d, u _q;

In steps d, described inverter work makes u _d=v _dand u _q=v _qoperation, specifically comprise:

Based on formula (8), make respectively i _d, i _qreference current value i _d*, i _q* all equal zero, controlling photovoltaic grid connection inverter output current is zero, obtains formula (9) and sets up:

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

Now show the voltage u of conversion to 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.

2. inverter according to claim 1 is connected the inhibition method of moment transformer magnetizing current with electrical network, it is characterized in that, before steps d, also comprises transformer is carried out to the operation of excitation in advance.

3. inverter according to claim 1 is connected the inhibition method of moment transformer magnetizing current with electrical network, it is characterized in that, the described line voltage by transformer primary side is converted grid side, the u being obtained by conversion _a, u _b, u _cthe conversion that is tied to two-phase synchronous rotating frame through three phase static coordinate obtains u _d, u _qoperation, specifically comprise:

Transformer adopting Δ/Y connection, supposes turn ratio n=Ns/Np, and wherein Ns, Np are respectively transformer secondary, the former limit number of turn, and n is natural number; By inverter output voltage V _ab, V _ca, V _bcto grid side, there is formula (3) in conversion:

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

Respectively by u _a, u _b, u _cand v _a, v _b, v _cand i _a, i _b, i _cthe conversion of carrying out being tied to by three phase static coordinate two-phase synchronous rotating frame obtains formula (4) and formula (5) and formula (6), and wherein, θ is by phase-locked loop:

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

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

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

Work as i _a, i _b, i _cwhile equalling zero, i.e. i _d, i _qalso equal zero, the each point voltage of circuit that is zero according to electric current equates, therefore photovoltaic combining inverter three-phase output voltage u _a, u _b, u _cconversion to the voltage of transformer secondary respectively with u _a, u _b, u _cequate, so formula (7) is set up:

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

In formula (7), wherein, L ₂the inductance value that filter inductance L converts transformer secondary, ω _gfor electrical network angular frequency;

the Δ v that can be obtained through proportional and integral controller by corresponding current error respectively _d, Δ v _qreplace, therefore have formula (8) to set up:

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

In formula (8), k _pfor proportionality coefficient, k _ifor integral coefficient, s is integral operator.

4. inverter is connected the inhibition system of moment transformer magnetizing current with electrical network, it is characterized in that, comprise classical three-phase inverting circuit IB, the three-phase filter inductance L, the grid-connected transformer TF of Δ/Y connection and the grid-connected switch S that are connected successively between photovoltaic array PV and electrical network Grid, be connected in parallel on the three-phase filter capacitor C between the grid-connected transformer TF of described three-phase filter inductance L and Δ/Y connection, and the judgement switch S adhesive algoritic module being connected between described three-phase filter inductance L and grid-connected switch S;

The course of work of described judgement switch S adhesive algoritic module, mainly comprises:

A, make inverter work, and to make the output current reference value of inverter under synchronous rotating frame be all zero;

Inverter output voltage and the line voltage of Δ/Y transformer secondary arrived in b, detection conversion;

C, the conversion detecting is carried out to three phase static coordinate system to two-phase synchronous rotating frame conversion to the inverter output voltage of Δ/Y transformer secondary, obtain u _d, u _q; The line voltage detecting is carried out to three phase static coordinate system to the conversion of two-phase synchronous rotating frame, obtain v _d, v _q;

D, make u when inverter work _d=v _dand u _q=v _qtime, show that at grid-connected switch the alternating voltage of grid-connected switch ends is synchronous before adhesive, amplitude, frequency and phase place are all identical, and the grid-connected switch of now adhesive can not produce larger static exciter impulse current;

Before steps d, also comprise transformer is carried out to the operation of excitation in advance;

In step b, the inverter output voltage of Δ/Y transformer secondary and the operation of line voltage are converted in described detection, specifically comprise:

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, described the conversion detecting is carried out to three phase static coordinate system to two-phase synchronous rotating frame conversion to the inverter output voltage of Δ/Y transformer secondary, obtain u _d, u _qoperation, specifically comprise:

Transformer adopting Δ/Y connection, supposes turn ratio n=Ns/Np, and wherein Ns, Np are respectively transformer secondary, the former limit number of turn, and n is natural number; By inverter output voltage V _ab, V _ca, V _bcto grid side, there is formula (3) in conversion:

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

Respectively by u _a, u _b, u _cand v _a, v _b, v _cand i _a, i _b, i _cthe conversion of carrying out being tied to by three phase static coordinate two-phase synchronous rotating frame obtains formula (4) and formula (5) and formula (6), and wherein, θ is by phase-locked loop:

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

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

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

Work as i _a, i _b, i _cwhile equalling zero, i.e. i _d, i _qalso equal zero, the each point voltage of circuit that is zero according to electric current equates, therefore photovoltaic combining inverter three-phase output voltage u _a, u _b, u _cconversion to the voltage of transformer secondary respectively with u _a, u _b, u _cequate, so formula (7) is set up:

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

In formula (7), wherein, L2 is the inductance value that filter inductance L converts transformer secondary, ω _gfor electrical network angular frequency;

the Δ v that can be obtained through proportional and integral controller by corresponding current error respectively _d, Δ v _qreplace, therefore have formula (8) to set up:

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

In formula (8), k _pfor proportionality coefficient, k _ifor integral coefficient, s is integral operator;

And/or,

In steps d, described inverter work makes u _d=v _dand u _q=v _qoperation, specifically comprise:

Based on formula (8), make respectively i _d, i _qreference current value i _d*, i _q* all equal zero, controlling photovoltaic grid connection inverter output current is zero, obtains formula (9) and sets up:

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

Now show the voltage u of conversion to 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.

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