CN102545677A - Parallel three-phase grid-connected inverter adopting mutual reactors and control method for three-phase grid-connected inverter - Google Patents
Parallel three-phase grid-connected inverter adopting mutual reactors and control method for three-phase grid-connected inverter Download PDFInfo
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Abstract
The invention discloses a parallel three-phase grid-connected inverter adopting mutual reactors and a control method for the three-phase grid-connected inverter, and belongs to the technical field of power grid inversion. The inverter overcomes the shortcomings of large volume, high weight, high cost, low efficiency, narrow application range, control complexity, low reliability and the like of the conventional parallel grid-connected inverter. According to the inverter, two sets of three-phase grid connected inverters are connected in parallel, and a capacitor is connected in parallel with a direct current bus which is shared by the two sets of three-phase grid connected inverters; and the two in-phase alternating current signal output ends of the two sets of three-phase grid-connected inverters are connected together after passing through a set of mutual reactor respectively, and are connected with a power grid. According to the three-phase grid-connected inverter, the two sets of three-phase grid-connected inverters with the same structure are coupled with each other by the mutual reactors; and for each three-phase grid-connected inverter, a d-axis component and a q-axis component are coupled with each other, and in order to eliminate the influence, a feed-forward decoupling control strategy and a current loop are adopted in the control method.
Description
Technical field
The invention belongs to electrical network inversion transformation technique field, be specifically related to three-phase grid-connected inverter.
Technical background
The enhancing of Along with people's environmental consciousness and the energy in short supply day by day is that the new forms of energy industry of representative has obtained significant progress with wind energy, solar energy etc.For the power delivery that will convert by wind energy, solar energy etc. to electrical network, need be converted into the corresponding to electric energy of amplitude, frequency, phase place and electrical network by combining inverter usually, thus being incorporated into the power networks of the system of realization.In order to improve the power grade of combining inverter, reduce production costs simultaneously, and improve system reliability, the parallel running of inverter has obtained extensive concern.Under the condition that does not increase single power switch current stress, through parallel technology total current is multiplied, research and develop more that the three-phase grid-connected inverter of high power level becomes a reality thereby make.In addition, under the certain situation of gross power, can use the lower device for power switching of power grade, thereby reduce production costs greatly.Simultaneously, parallelly connected scheme is convenient to carry out modularized design, has shortened the production cycle, and has widened the scope of application of power model.And (carrier phase shift CPS) after the technology, can make the harmonic wave of parallel connection back total current reduce greatly, and then can reduce filter capacity, has reduced production cost to adopt carrier phase.In addition, parallelly connected scheme makes the N+1 Redundancy Design become a reality, and has improved the reliability of system, in conjunction with hot-plugging technology, makes it have greater advantages.
In single cover converter system,, there is not circulation problem, but in the parallel connection type system,, will produces serious circulation problem if there is circulation channel owing to there is not the zero sequence circulation channel.Circulation only flows between the current transformer of parallel connection, and its existence has increased loss, has reduced system effectiveness, and makes the power device heating serious, even it is burnt.And circulation can cause uneven flow problem, thereby the current stress that power device is born is unbalanced, influences its useful life, and limited the increase of whole system capacity.Circulation can make three-phase current produce distortion simultaneously, makes that (total harmonicdistortion THD) increases total percent harmonic distortion, causes system can not satisfy the requirement of being incorporated into the power networks.In addition, high frequency circulation can bring serious electromagnetic interference (electromagnetic interface, EMI) problem.
For solving circulation problem, Chinese scholars is furtherd investigate.Traditionally, adopt AC side to use isolating transformer scheme or suitable software scenario usually to suppress zero sequence circulation.
Document 1 (Dixon J W; Ooi B T.Series and parallel operation of hysteresis current-controlledPWM rectifiers [J] .IEEE Transaction on Industry Applications; 1989; 25 (4): 644-651) that a plurality of structures are identical converter parallel connection is used, and AC side is isolated the input of each converter through isolating transformer, has improved the power grade of converter; Eliminated the zero sequence circulation problem, but the use of isolating transformer volume, weight and the cost of system have been increased greatly.
Document 2 (Yoshihiro Komatsuzaki.Cross current control for parallel operating three phaseinverter [C] .Power Electronics Specialists Conference; Taipei; China, 1994) and document 3 (SFukuda, K Matsushita.A control method for parallel-connected multiple inverter systems.PowerElectronics and Variable Speed Drive; London; England, 1998) parallel connection converter is used as an integral body and controls, suppressed circulation from control method; But this mode is controlled complicacy, when more multimode is parallelly connected, is difficult to realize.
Document 4 (Li Jianlin, Gao Zhigang, Hu Shuju; Deng. parallel connection back-to-back the PWM current transformer in the application [J] of direct-driving type wind power generation system. Automation of Electric Systems, 2008,32 (5): 59-62) proposed the topological structure of independent direct current bus; On hardware, eliminated circulation channel, solved circulation problem, and it is simple relatively that system is controlled; But this topological structure only is applicable to the specific type of electric machine with electrical isolation effect; When still there is serious circulation problem in motor during for commonly used three phase electric machine, and pusher side circulation intercouples with net side ring stream, limited its use occasion.In addition, this topological structure must be controlled respectively two busbar voltages because dc bus separates, and has increased the volume of system, and has been unfavorable for modularized design.
Document 5 (Li Rui, Xu Zhuan, Xu Dianguo. the CIRCULATION ANALYSIS of parallel-type permanent magnet direct wind dispelling electric system and control [J] thereof. Proceedings of the CSEE; 2011,31 (6): 38-45) proposed the parallel connection type converter topologies, AC side has been saved isolating transformer; Design zero sequence circulator controller simultaneously, suppressed zero sequence circulation, improved the power grade of current transformer greatly; But because the impedance of zero sequence circulation is less; Therefore to solve difficulty relatively large for the zero sequence circulation problem, and in addition, the use of zero sequence circulation controller has increased the complexity of control system.
Summary of the invention
Deficiencies such as traditional parallel connection type combining inverter volume weight is big, cost is high, efficient is low in order to overcome, narrow in application range, control complicacy, poor reliability the present invention proposes a kind of parallel connection type three-phase grid-connected inverter of mutual reactor and control method of this three-phase grid-connected inverter of adopting.
The parallel connection type three-phase grid-connected inverter of employing mutual reactor of the present invention is made up of two nested structures identical three-phase grid-connected inverter and three cover mutual reactors; The shared altogether dc bus of the three-phase grid-connected inverter that said two nested structures are identical is on the said dc bus and connect capacitor; The three-phase grid-connected inverter connection parallel with one another that said two nested structures are identical, two AC signal outputs that belong to same phase in the identical three-phase grid-connected inverter of two nested structures connect together behind a cover mutual reactor respectively, and insert electrical network.
Power switch in the identical three-phase grid-connected inverter of said two nested structures adopts IGBT to realize.
The control method of above-mentioned three-phase grid-connected inverter is: the DC bus-bar voltage signal that adopts voltage sensor measurement acquisition is as direct voltage feedback quantity U
Dc, DC bus-bar voltage set-point U
DcrefWith direct voltage feedback quantity U
DcInput to Voltage loop PI controller after doing difference, after this Voltage loop PI controller is handled, obtain i
Dref, this i
DrefAfter weight allocation, obtain two electric current set-point i
D1ref, i
D2ref, said two electric current set-point i
D1ref, i
D2refRespectively as the be incorporated into the power networks electric current set-point of d shaft current ring controller of three-phase inverter of two covers;
Simultaneously, the employing current sensor is measured the three-phase current signal that obtains two cover combining inverters respectively, and this three-phase current signal is obtained the d shaft current i of said two cover combining inverters after coordinate transform
D1, i
D2With q shaft current i
Q1, i
Q2Said d shaft current i
D1, i
D2With q shaft current i
Q1, i
Q2Realize the closed-loop control of d shaft current ring and the closed-loop control of q shaft current as the value of feedback of d shaft current ring and the value of feedback of q shaft current ring respectively;
The value of feedback i of each d shaft current ring
D1, i
D2Respectively with current corresponding set-point i
D1ref, i
D2refDo difference after after the PI adjusting, carry out addition with corresponding feedforward compensation amount respectively again and obtain u
D1, u
D2
The value of feedback i of each q shaft current ring
Q1, i
Q2Respectively with current corresponding set-point i
Q1ref, i
Q2refDo difference after after the PI adjusting, carry out addition with corresponding feedforward compensation amount respectively again and obtain u
Q1, u
Q2
Said u
D1, u
D2And u
Q1, u
Q2Output signal as current loop controller; Said output signal obtains the Voltage Reference amount in the two phase rest frames after the Park inverse transformation; This Voltage Reference amount generates the duty cycle signals of three-phase brachium pontis as the input of SVPWM module; And then obtain be incorporated into the power networks six tunnel controls of three-phase inverter of two covers and use pwm signal, realization is to the control of combining inverter.
In the three-phase grid-connected inverter of the present invention because the use of mutual reactor; Make coupling mutually between the identical three-phase grid-connected inverter of two nested structures; And concerning every three-phase grid-connected inverter; Also exist between d axle, the q axle component to intercouple, for eliminating these influences, the present invention has adopted the feedforward decoupling control policy when the design current ring.
Because said two cover three-phase grid-connected inverters are connected in parallel, therefore said two cover three-phase grid-connected inverters use common outer voltage, independent current inner loop.
The given i of electric current of q shaft current ring controller in the above-mentioned control method
Q1ref, i
Q2refBe generally zero, maximum to guarantee the ability that under the certain situation of capacity combining inverter presents active power to electrical network, and realize that unity power factor is incorporated into the power networks the given i of q shaft current
Q1ref, i
Q2refAlso can be provided idle demand by electrical network, the realization system is to the reactive power compensation of electrical network.
The power grade of inverter according to the invention increases to original twice, and has simplified the design of control system, and has saved isolating transformer; Greatly reduce the volume and weight of current transformer; Reduce cost, suppressed zero sequence circulation simultaneously, solved problems such as the not current-sharing that zero sequence circulation causes, wave distortion; Improved efficient and reliability, made the parallel connection type three-phase grid-connected inverter can be applicable to occasions such as high-power wind power generation, solar power generation and gas turbine power generation.
The present invention adopts the parallelly connected scheme of mutual reactor; At first; Mutual reactor only has damping action to the differential-mode component of parallel connection converter branch current, its common mode component is not had damping action, so it has the autonomous equalizing current effect; Thereby each parallel connection converter current stress is reached unanimity, thereby be that the power grade that promotes converter lays the first stone.Simultaneously, two shunt chopper branch currents equate in the ideal case, for the mutual reactor of heteropleural parallel connection, do not produce magnetic flux, therefore compare with traditional reactor, and the volume of mutual reactor can reduce greatly.In addition, mutual reactor can be realized the inhibition to zero sequence circulation.
Characteristics of the present invention are: through mutual reactor the identical three-phase grid-connected inverter of two nested structures is connected in parallel, makes the power grade of inverter increase to original twice; Two shunt choppers adopt identical control structure, have simplified the design of control system; Owing to saved isolating transformer, reduced the volume and weight of current transformer greatly, reduced cost; Suppressed circulation simultaneously, solved problems such as not current-sharing between two parallel connection converters, wave distortion, improved efficient and reliability, made the parallel connection type three-phase grid-connected inverter can be applicable to occasions such as high-power wind power generation, solar power generation and gas turbine power generation.
Description of drawings
Fig. 1 is the topological structure of the parallel connection type three-phase grid-connected inverter of employing mutual reactor of the present invention.
Fig. 2 is the equivalent circuit theory figure that decouples of topological structure of the parallel connection type three-phase grid-connected inverter of employing mutual reactor of the present invention.
Fig. 3 is the equivalent circuit theory figure of topological structure under synchronous rotating frame of the parallel connection type three-phase grid-connected inverter of employing mutual reactor of the present invention.
Fig. 4 is the control principle figure of the control method of three-phase grid-connected inverter of the present invention.
Embodiment
Embodiment one, referring to Fig. 1,2 and 3 the explanation these execution modes; The parallel connection type three-phase grid-connected inverter of the described employing mutual reactor of this execution mode is made up of two nested structures identical three-phase grid-connected inverter and three cover mutual reactors; The shared altogether dc bus of the three-phase grid-connected inverter that said two nested structures are identical is on the said dc bus and connect capacitor; The three-phase grid-connected inverter connection parallel with one another that said two nested structures are identical, two AC signal outputs that belong to same phase in the identical three-phase grid-connected inverter of two nested structures connect together behind a cover mutual reactor respectively, and insert electrical network.
Power switch in the identical three-phase grid-connected inverter of two nested structures described in this execution mode can adopt IGBT to realize.
The topological structure of the parallel connection type three-phase grid-connected inverter of the described employing mutual reactor of this execution mode is referring to shown in Figure 1; The electric energy that prime is carried is sent into back level parallel connection type three-phase grid-connected inverter through on the shared common dc bus and after the capacitor C filtering, energy storage and the voltage stabilizing that connect.Every cover three-phase grid-connected inverter is made up of three brachium pontis, and wherein three brachium pontis of the first cover three-phase grid-connected inverter are respectively A
1, B
1, C
1, three brachium pontis of the second cover three-phase grid-connected inverter are respectively A
2, B
2, C
2, two cover three-phase grid-connected inverters are parallel with one another, and each ac output end of every cover three-phase grid-connected inverter is respectively through inductance L
K1And L
K2(k=a, b connect together after c), and then insert electrical network.Inductance L
K1And L
K2Between have coupling, mutual inductance is M
k(k=a, b c), and are the heteropleural parallel circuits; R
Ak, R
Bk, R
CkWhat (k=1,2) were respectively k cover three-phase grid-connected inverter comprises inductance resistance at interior every phase line resistance; U
DcBus direct voltage for shared common dc bus.
Referring to the equivalent electric circuit of decoupling of topological structure shown in Figure 1 shown in Figure 2, L among the figure
Ak'=L
Ak+ M
a, L
Bk'=L
Bk+ M
b, L
Ck'=L
Ck+ M
c(k=1,2), and get L usually
Ak=L
Bk=L
Ck=L
k, R
Ak=R
Bk=R
Ck=R
k(k=1,2), M
a=M
b=M
c=M; i
1Be the direct current that prime transmitted; i
Ak, i
Bk, i
Ck(k=1,2) are respectively the three-phase grid branch current of k cover three-phase grid-connected inverter; e
a, e
b, ec is respectively the electrical network three-phase voltage.
Can not be too small when choosing mutual inductance M can not be excessive, when too small, can reduce the effect that mutual reactor suppresses zero sequence circulation; When excessive; Can increase the coupling between two shunt choppers, and then increase the difficulty of control, consider through balance; The representative value that the present invention gets coupling coefficient k is 0.415, and then mutual inductance M is:
K is a coupling coefficient in the above-mentioned formula, L
1Be the three-phase self-induction of the first cover three-phase grid-connected inverter, L
2It is the three-phase self-induction of the second cover three-phase grid-connected inverter.
Referring to equivalent electric circuit under the synchronous rotating frame of topological structure shown in Figure 1 shown in Figure 3, L among the figure
k'=L
Ak'=L
Bk'=L
Ck' (k=1,2); i
Dk, i
Qk(k=1,2) are respectively d axle, the q axle branch current that is incorporated into the power networks; d
Dk, d
Qk, d
Zk(k=1,2) are respectively d axle, q axle, z axle duty ratio; e
d, e
qBe respectively electrical network d axle, q shaft voltage; ω is a synchronized angular speed.
As can beappreciated from fig. 3, d shaft current component i
D1, i
D2Through inductance-M and controlled voltage source (ω Mi
q) be coupled to together, this has increased the difficulty of control.Because d axle, q axle have symmetry, therefore can draw like conclusion for q shaft current component.Z axle equivalent electric circuit can find out that the impedance of zero sequence circulation is (L from figure
1+ L
2+ R
1+ R
2+ 2M), formula R
1Be first the cover three-phase grid-connected inverter comprise inductance resistance at interior three-phase line equivalent resistance, R
2Be second the cover three-phase grid-connected inverter comprise inductance resistance at interior three-phase line equivalent resistance.And the impedance of zero sequence circulation is merely (L when adopting common three-phase reactor
1+ L
2+ R
1+ R
2), therefore when adopting mutual reactor the resistance of zero sequence circulation bigger, played the effect that suppresses zero sequence circulation, especially more obvious to high frequency zero sequence circulation effect.Heavy isolating transformer and the complicated zero sequence circulation controller of AC side saved in its use, reduced production cost, reduced volume, the weight of combining inverter, and simplified the design of control system, promoted the performance of combining inverter.
Definition i
ZsBe system's zero sequence circulation of parallel connection type three-phase grid-connected inverter, and
i
zs＝i
z1＝-i
z2 (2)
Then zero sequence circulation can further be expressed as respectively:
Embodiment two, this execution mode is described referring to Fig. 4.This execution mode is described to be the control method to the parallel connection type three-phase grid-connected inverter of embodiment one described employing mutual reactor; Said control method is: the DC bus-bar voltage signal that adopts voltage sensor measurement acquisition is as direct voltage feedback quantity Udc; DC bus-bar voltage set-point Udcref and direct voltage feedback quantity Udc input to Voltage loop PI controller after doing difference;, this Voltage loop PI controller obtains idref after handling; This idref obtains two electric current set-point id1ref, id2ref after weight allocation, said two electric current set-point id1ref, id2ref are respectively as the be incorporated into the power networks electric current set-point of d shaft current ring controller of three-phase inverter of two covers;
Simultaneously, the employing current sensor is measured the three-phase current signal that obtains two cover combining inverters respectively, and this three-phase current signal is obtained the d shaft current i of said two cover combining inverters after coordinate transform
D1, i
D2With q shaft current i
Q1, i
Q2Said d shaft current i
D1, i
D2With q shaft current i
Q1, i
Q2Realize the closed-loop control of d shaft current ring and the closed-loop control of q shaft current as the value of feedback of d shaft current ring and the value of feedback of q shaft current ring respectively;
The value of feedback i of each d shaft current ring
D1, i
D2Respectively with current corresponding set-point i
D1ref, i
D2refDo difference after after the PI adjusting, carry out addition with corresponding feedforward compensation amount respectively again and obtain u
D1, u
D2
The value of feedback i of each q shaft current ring
Q1, i
Q2Respectively with current corresponding set-point i
Q1ref, i
Q2refDo difference after after the PI adjusting, carry out addition with corresponding feedforward compensation amount respectively again and obtain u
Q1, u
Q2
Said u
D1, u
D2And u
Q1, u
Q2Output signal as current loop controller; Said output signal obtains the Voltage Reference amount in the two phase rest frames after the Park inverse transformation; This Voltage Reference amount generates the duty cycle signals of three-phase brachium pontis as the input of SVPWM module; And then obtain be incorporated into the power networks six tunnel controls of three-phase inverter of two covers and use pwm signal, realization is to the control of combining inverter.
Embodiment three, this execution mode are the further qualifications to embodiment two described control methods; In this execution mode; The process of said weight allocation is: the power capacity according to two cover three-phase inverters carries out the current weights distribution; If the power capacity of two cover three-phase inverters equates, then carry out equivalence and distribute, be i.e. i
D1ref=i
D2ref=0.5i
DrefIf the power capacity of two cover three-phase inverters is unequal, then distribute in proportion, i.e. i according to power capacity
D1ref=ji
Dref, i
D2ref=(1-j) i
Dref, j is the power capacity ratio of two cover three-phase inverters.
Embodiment four, this execution mode are the further qualifications to embodiment two described control methods, in this execution mode, and the given i of electric current of said q shaft current ring controller
Q1ref, i
Q2refValue is 0.
Embodiment five, this execution mode are the further qualifications to embodiment two described control methods, in this execution mode, and the value of feedback i of said each d shaft current ring
D1, i
D2Respectively with current corresponding set-point i
D1ref, i
D2refDo difference after after the PI adjusting, carry out addition with corresponding feedforward compensation amount respectively again and obtain u
D1, u
D2, the feedforward compensation amount of said correspondence is respectively e
d+ ω L
1' i
Q1-ω Mi
qAnd e
d+ ω L
2' i
Q2-ω Mi
q, e
dBe line voltage d axle feedforward component, ω is a synchronized angular speed; L
1' be the three-phase branch road equivalent inductance of the first cover three-phase grid-connected inverter; L
2' be the three-phase branch road equivalent inductance of the second cover three-phase grid-connected inverter; M is the three-phase mutual inductance between the two cover three-phase inverters.
Embodiment six, this execution mode are the further qualifications to embodiment two described control methods, in this execution mode, and the value of feedback i of each q shaft current ring
Q1, i
Q2Respectively with current corresponding set-point i
Q1ref, i
Q2refDo difference after after the PI adjusting, carry out addition with corresponding feedforward compensation amount respectively again and obtain u
Q1, u
Q2, the feedforward compensation amount of said correspondence is respectively ω L
1' i
D1-ω Mi
dWith ω L
2' i
D2-ω Mi
d, ω is a synchronized angular speed; L
1' be the three-phase branch road equivalent inductance of the first cover three-phase grid-connected inverter; L
2' be the three-phase branch road equivalent inductance of the second cover three-phase grid-connected inverter; M is the three-phase mutual inductance between the two cover three-phase inverters.
Embodiment seven, this execution mode are the further qualifications to embodiment two described control methods, in this execution mode, and said u
D1, u
D2And u
Q1, u
Q2Output signal as current loop controller; Said output signal obtains the Voltage Reference amount in the two phase rest frames after the Park inverse transformation; This Voltage Reference amount generates the duty cycle signals of three-phase brachium pontis as the input of SVPWM module, and then obtains be incorporated into the power networks six tunnel controls of three-phase inverter of two covers and use the process of pwm signals to be: said u
D1And u
Q1After the Park inverse transformation, obtain the Voltage Reference amount u in the two phase rest frames
α 1, u
β 1, said Voltage Reference amount u
α 1, u
β 1As the input signal of SVPWM module, control this SVPWM module and generate three-phase duty cycle signals d
A1, d
B1, d
C1, according to said three-phase duty cycle signals d
A1, d
B1, d
C1Generate 6 road PWM ripples, after this 6 road PWM ripple amplifies as 6 road PWM drive signals of a cover three-phase grid-connected inverter; Voltage u
D2, u
Q2After the Park inverse transformation, obtain the Voltage Reference amount u in the two phase rest frames
α 2, u
β 2, said Voltage Reference amount u
α 2, u
β 2As the input signal of SVPWM module, control this SVPWM module and generate three-phase duty cycle signals d
A2, d
B2, d
C2, according to said three-phase duty cycle signals d
A2, d
B2, d
C2Generate 6 road PWM ripples, after this 6 road PWM ripple amplifies as 6 road PWM drive signals of another set of three-phase grid-connected inverter.
Because said two cover three-phase grid-connected inverters use common outer voltage, current inner loop independently; So; The effect of Voltage loop mainly is keep DC bus-bar voltage stable; Thereby make energy be transported to electrical network from DC side, its output is after current weights is distributed, respectively as the given i of d shaft current of two cover three-phase grid-connected inverters
D1ref, i
D2refUnder the certain situation of three-phase grid-connected inverter capacity, for energy delivery is arrived electrical network, the given i of q shaft current of two cover three-phase grid-connected inverters the biglyyest
Q1ref, i
Q2refGenerally be made as zero, thereby realize that unity power factor is incorporated into the power networks.i
Q1ref, i
Q2refAlso can provide by the palpus reactive requirement of electrical network to system.
Because there is symmetry in two covers between the three-phase grid-connected inverters, and also have symmetry between the electric current loop d axle, q axle component, d axle, the q shaft current ring controller of therefore said two cover three-phase grid-connected inverters can use identical Control Parameter.
Because the use of mutual reactor; Make to be coupled mutually between the two cover three-phase grid-connected inverters, and concerning every cover three-phase grid-connected inverter, also exist between d axle, the q axle component to intercouple; For eliminating these influences, when the design current ring, need adopt the feedforward decoupling control policy.D shaft current ring controller with the first cover three-phase grid-connected inverter is an example, with decoupling zero item (ω L
1' i
Q1-ω Mi
q) compensate to the output of pi regulator, can play the effect of decoupling zero between two combining inverters again so that realize decoupling zero between the d axle, q axle component.In addition, line voltage d axle feedforward component e
dOffset the influence of line voltage in the reality, and then obtained the d axle output reference voltage u of the first cover three-phase grid-connected inverter
D1After obtaining d axle, q axle output reference voltage, send into the SVPWM module through the coordinate inverse transformation, and then obtain the three-phase duty cycle signals, thereby realize control combining inverter.
In the above-mentioned control method, said Voltage loop PI controller by two cover three-phase grid-connected inverters the Voltage loop controller of the common outer voltage of use.
The principle of above-mentioned control method is:
The employing current sensor is measured the three-phase current signal i that the three-phase current signal that obtains two cover combining inverters is respectively the first cover three-phase grid-connected inverter respectively
A1, i
B1And i
C1, the three-phase current signal i of the second cover three-phase grid-connected inverter
A2, i
B2, i
C2,, said three-phase voltage is respectively u
a, u
b, u
c
Above-mentioned electric current and voltage parameter obtain physical quantity corresponding i under the synchronous rotating frame through coordinate transform
D1, i
Q1, i
Z1, i
D2, i
Q2, i
Z2, u
d, u
q, wherein, i
D1, i
D2As the feedback of d shaft current ring controller, respectively with set-point i
D1ref, i
D2refDo difference after PI regulates, add compensation rate (e separately
d+ ω L
1' i
Q1-ω Mi
q), (e
d+ ω L
2' i
Q2-ω Mi
q) back output voltage reference quantity u as d shaft current ring controller
D1, u
D2The electric current of q shaft current ring controller is given to be generally zero, i.e. i
Q1ref=i
Q2ref=0, maximum to guarantee the ability that under the certain situation of capacity combining inverter presents active power to electrical network, and realize that unity power factor is incorporated into the power networks i
Q1ref, i
Q2refAlso can provide idle demand by electrical network, thus the realization system to the reactive power compensation of electrical network, present embodiment adopts the former mode.Value of feedback i
Q1, i
Q2Respectively with i
Q1ref, i
Q2refDo difference after PI regulates, add compensation rate (ω L separately
1' i
D1-ω Mi
d), (ω L
2' i
D2-ω Mi
d) back output voltage reference quantity u as q shaft current ring controller
Q1, u
Q2Voltage Reference amount u
D1, u
Q1After the Park inverse transformation, obtain the Voltage Reference amount u in the two phase rest frames
α 1, u
β 1, input generates three-phase duty cycle signals d as the SVPWM module
A1, d
B1, d
C1Thereby, generate 6 road PWM ripples,, optical fiber delivers to drive plate after isolating, finally obtain 6 road PWM drive signals of the first cover three-phase grid-connected inverter.Voltage Reference amount u
D2, u
Q2After the Park inverse transformation, obtain the Voltage Reference amount u in the two phase rest frames
α 2, u
β 2, input obtains three-phase duty cycle signals d as the SVPWM module
A2, d
B2, d
C2Thereby, generate 6 road PWM ripples,, optical fiber delivers to drive plate after isolating, finally obtain 6 road PWM drive signals of the second cover three-phase grid-connected inverter.
Claims (8)
1. adopt the parallel connection type three-phase grid-connected inverter of mutual reactor; It is characterized in that; It is made up of identical three-phase grid-connected inverter of two nested structures and three cover mutual reactors, and the shared common dc bus of the three-phase grid-connected inverter that said two nested structures are identical is on the said dc bus and connect capacitor; The three-phase grid-connected inverter connection parallel with one another that said two nested structures are identical, two AC signal outputs that belong to same phase in the identical three-phase grid-connected inverter of two nested structures connect together behind a cover mutual reactor respectively, and insert electrical network.
2. the parallel connection type three-phase grid-connected inverter of employing mutual reactor according to claim 1 is characterized in that, the power switch in the identical three-phase grid-connected inverter of said two nested structures adopts IGBT to realize.
3. the control method of the parallel connection type three-phase grid-connected inverter of the described employing mutual reactor of claim 1 is characterized in that, the DC bus-bar voltage signal that adopts voltage sensor measurement acquisition is as direct voltage feedback quantity U
Dc, DC bus-bar voltage set-point U
DcrefWith direct voltage feedback quantity U
DcInput to Voltage loop PI controller after doing difference, after this Voltage loop PI controller is handled, obtain i
Dref, this i
DrefAfter weight allocation, obtain two electric current set-point i
D1ref, i
D2ref, said two electric current set-point i
D1ref, i
D2refRespectively as the be incorporated into the power networks electric current set-point of d shaft current ring controller of three-phase inverter of two covers;
Simultaneously, the employing current sensor is measured the three-phase current signal that obtains two cover combining inverters respectively, and this three-phase current signal is obtained the d shaft current i of said two cover combining inverters after coordinate transform
D1, i
D2With q shaft current i
Q1, i
Q2Said d shaft current i
D1, i
D2With q shaft current i
Q1, i
Q2Realize the closed-loop control of d shaft current ring and the closed-loop control of q shaft current as the value of feedback of d shaft current ring and the value of feedback of q shaft current ring respectively;
The value of feedback i of each d shaft current ring
D1, i
D2Respectively with current corresponding set-point i
D1ref, i
D2refDo difference after after the PI adjusting, carry out addition with corresponding feedforward compensation amount respectively again and obtain u
D1, u
D2
The value of feedback i of each q shaft current ring
Q1, i
Q2Respectively with current corresponding set-point i
Q1ref, i
Q2refDo difference after after the PI adjusting, carry out addition with corresponding feedforward compensation amount respectively again and obtain u
Q1, u
Q2
Said u
D1, u
D2And u
Q1, u
Q2Output signal as current loop controller; Said output signal obtains the Voltage Reference amount in the two phase rest frames after the Park inverse transformation; This Voltage Reference amount generates the duty cycle signals of three-phase brachium pontis as the input of SVPWM module; And then obtain be incorporated into the power networks six tunnel controls of three-phase inverter of two covers and use pwm signal, realization is to the control of combining inverter.
4. the control method of the parallel connection type three-phase grid-connected inverter of employing mutual reactor according to claim 3; It is characterized in that; The process of wherein said weight allocation is: the power capacity according to two cover three-phase inverters carries out the current weights distribution; If the power capacity of two cover three-phase inverters equates, then carry out equivalence and distribute, be i.e. i
D1ref=i
D2ref=0.5i
DrefIf the power capacity of two cover three-phase inverters is unequal, then distribute in proportion, i.e. i according to power capacity
D1ref=ji
Dref, i
D2ref=(1-j) i
Dref, j is the power capacity ratio of two cover three-phase inverters.
5. the control method of the parallel connection type three-phase grid-connected inverter of employing mutual reactor according to claim 3 is characterized in that, the given i of electric current of said q shaft current ring controller
Q1ref, i
Q2refValue is 0.
6. the control method of the parallel connection type three-phase grid-connected inverter of employing mutual reactor according to claim 3 is characterized in that, the value of feedback i of said each d shaft current ring
D1, i
D2Respectively with current corresponding set-point i
D1ref, i
D2refDo difference after after the PI adjusting, carry out addition with corresponding feedforward compensation amount respectively again and obtain u
D1, u
D2, the feedforward compensation amount of said correspondence is respectively e
d+ ω L
1' i
Q1-ω Mi
qAnd e
d+ ω L
2' i
Q2-ω Mi
q, e
dBe line voltage d axle feedforward component, ω is a synchronized angular speed; L
1' be the three-phase branch road equivalent inductance of the first cover three-phase grid-connected inverter; L
2' be the three-phase branch road equivalent inductance of the second cover three-phase grid-connected inverter; M is the three-phase mutual inductance between the two cover three-phase inverters.
7. the control method of the parallel connection type three-phase grid-connected inverter of employing mutual reactor according to claim 3 is characterized in that, the value of feedback i of each q shaft current ring
Q1, i
Q2Respectively with current corresponding set-point i
Q1ref, i
Q2refDo difference after after the PI adjusting, carry out addition with corresponding feedforward compensation amount respectively again and obtain u
Q1, u
Q2, the feedforward compensation amount of said correspondence is respectively ω L
1' i
D1-ω Mi
dWith ω L
2' i
D2-ω Mi
d, ω is a synchronized angular speed; L
1' be the three-phase branch road equivalent inductance of the first cover three-phase grid-connected inverter; L
2' be the three-phase branch road equivalent inductance of the second cover three-phase grid-connected inverter; M is the three-phase mutual inductance between the two cover three-phase inverters.
8. the control method of the parallel connection type three-phase grid-connected inverter of employing mutual reactor according to claim 3 is characterized in that, said u
D1, u
D2And u
Q1, u
Q2Output signal as current loop controller; Said output signal obtains the Voltage Reference amount in the two phase rest frames after the Park inverse transformation; This Voltage Reference amount generates the duty cycle signals of three-phase brachium pontis as the input of SVPWM module, and then obtains be incorporated into the power networks six tunnel controls of three-phase inverter of two covers and use the process of pwm signals to be: said u
D1And u
Q1After the Park inverse transformation, obtain the Voltage Reference amount u in the two phase rest frames
α 1, u
β 1, said Voltage Reference amount u
α 1, u
β 1As the input signal of SVPWM module, control this SVPWM module and generate three-phase duty cycle signals d
A1, d
B1, d
C1, according to said three-phase duty cycle signals d
A1, d
B1, d
C1Generate 6 road PWM ripples, after this 6 road PWM ripple amplifies as 6 road PWM drive signals of a cover three-phase grid-connected inverter; Voltage u
D2, u
Q2After the Park inverse transformation, obtain the Voltage Reference amount u in the two phase rest frames
α 2, u
β 2, said Voltage Reference amount u
α 2, u
β 2As the input signal of SVPWM module, control this SVPWM module and generate three-phase duty cycle signals d
Q2, d
B2, d
C2, according to said three-phase duty cycle signals d
A2, d
B2, d
C2Generate 6 road PWM ripples, after this 6 road PWM ripple amplifies as 6 road PWM drive signals of another set of three-phase grid-connected inverter.
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