CN104201923B - Three-phase four-arm isolated form inverter control method - Google Patents

Abstract

The invention discloses a kind of three-phase four-arm isolated form inverter and control method thereof, described inverter includes input filter capacitor, inverter bridge leg, isolating transformer, diode brachium pontis, the two-way switch group of four two-way switch compositions, three-phase four-arm, output filter.The present invention uses the three-dimensional space vector modulation method of improvement to control changer, it is achieved the voltage-second balance of transformator and power conversion.The present invention solves the three-phase inverter of band unbalanced load in prior art and can not realize high frequency electrical isolation and realize the problem that the inverter of high frequency electrical isolation does not possess band unbalanced load ability at present.

Description

Three-phase four-arm isolated form inverter control method

Technical field

The present invention relates to three-phase inverter, particularly relate to a kind of three-phase four-arm isolated form inverter and control method thereof.

Background technology

Three-phase inverter is powered to threephase load under independent operation mode, and its output voltage should meet the condition that each phase amplitude is equal and each phase phase contrast is 120 degree.If three-phase voltage can not meet the condition of amplitude and phase place simultaneously, then three-phase output voltage is considered uneven.Imbalance of three-phase voltage is caused to have two main causes: three-phase circuit parameter unbalance and threephase load are asymmetric.Electrical equipment and power supply unit can be caused many unfavorable factors by imbalance of three-phase voltage.Under serious conditions, the permanent damage of equipment may be caused.Therefore, three-phase voltage equilibrium condition is one of important indicator of the quality of power supply, and in some specific occasions, three-phase inverter must have the ability of band asymmetric load, and i.e. in the case of threephase load is asymmetric, three-phase voltage remains in that balance.

Research for the suppression of three-phase inverter imbalance is concentrated mainly on two aspects of topological sum control strategy.Control strategy is more, and the research of topology is relatively fewer, relatively common three-phase inverter topology has five kinds: split capacitor formula inverter topology, three phase full bridge band triangle star isolating transformer inverter topology, three-phase half-bridge inverter topological sum three-phase four-leg inverter topology.By rational control strategy, these topologys all can meet the electrical equipment requirement to non-equilibrium among three phase voltages.Wherein, three-phase four-arm inversion topological is that Recent study compares a kind of inverter structure widely, has that circuit form is simple, volume is little, DC voltage utilization rate advantages of higher.And the control mode that three-phase four-arm inversion topological is commonly used has: according to current in middle wire direction controlling four bridge legs, maximum error circuit regulation method, neutral point potential control methods, phase sequence control method and three-dimensional space vector modulation method.Three-dimensional space vectors controls lower three-phase four-leg inverter, has that DC voltage utilization rate is high, it is flexible to control, be easy to the advantages such as digital control realization.But, it solve only the problem that conventional three-phase full-bridge inverter does not have band unbalanced load ability.In some occasions needing to realize electrical isolation, three-phase four-leg inverter is not carried out high frequency electrical isolation, needs to use Industrial Frequency Transformer to realize electrical isolation at outfan, so can increase volume and the cost of changer.And three-dimensional space vectors control method is also only applicable to the three-phase four-arm inversion topological of non-isolated accordingly.

Summary of the invention

It is an object of the invention to provide a kind of three-phase four-arm isolated form inverter and control method thereof, solve the three-phase inverter of band unbalanced load in prior art and can not realize high frequency electrical isolation and realize the problem that the inverter of high frequency electrical isolation does not possess band unbalanced load ability at present.

The present invention is adopted the technical scheme that for achieving the above object: a kind of three-phase four-arm isolated form inverter, it is characterized in that including: input filter capacitor, inverter bridge leg, isolating transformer, diode brachium pontis, the two-way switch group of four two-way switch compositions, three-phase four-arm, output filter；Inverter bridge leg is in parallel with input filter capacitor, and two brachium pontis midpoints of inverter bridge leg are connected with isolating transformer primary side winding two ends respectively；Diode brachium pontis is in parallel with three-phase four-arm, one end with four two-way switch respectively, four brachium pontis midpoints of three-phase four-arm is connected, the other end of four two-way switch is all connected with isolating transformer vice-side winding Same Name of Ends, and diode brachium pontis midpoint is connected with isolating transformer vice-side winding different name end；Output filter is LC wave filter, is made up of four filter inductances and three filter capacitors；Midpoint with in three-phase four-arm four brachium pontis respectively, one end of four filter inductances is connected, and wherein connect in the other end of three filter inductances one end with three output filter capacitors respectively, and three output filter capacitor other ends are connected, and constitute output ground；Threephase load is in parallel with three output filter capacitors respectively；Another termination output ground of 4th filter inductance.

Described inverter bridge leg is made up of four switching tubes, the emitter stage of the first switching tube is connected as a brachium pontis with the colelctor electrode of second switch pipe, the emitter stage of the 3rd switching tube and the colelctor electrode of the 4th switching tube are connected as a brachium pontis, first switching tube, the colelctor electrode of the 3rd switching tube are connected, and second switch pipe, the emitter stage of the 4th switching tube are connected.

Described diode brachium pontis is made up of two diodes, and the anode of the first diode and the negative electrode of the second diode are connected.

Described two-way switch group is made up of eight switching tubes, the emitter stage of the 5th switching tube and the emitter stage of the 6th switching tube are connected to form a two-way switch, the emitter stage of the 7th switching tube and the emitter stage of the 8th switching tube are connected to form a two-way switch, the emitter stage of the 9th switching tube and the emitter stage of the tenth switching tube are connected to form a two-way switch, and the emitter stage of the 11st switching tube and twelvemo are closed the emitter stage of pipe and be connected to form a two-way switch.

Described three-phase four-arm is made up of eight switching tubes, the emitter stage of the 13rd switching tube and the colelctor electrode of the 14th switching tube are connected as a brachium pontis, the emitter stage of the 15th switching tube and sixteenmo close the colelctor electrode of pipe and are connected as a brachium pontis, the emitter stage of the 17th switching tube and eighteenmo close the colelctor electrode of pipe and are connected as a brachium pontis, the emitter stage of the 19th switching tube and the colelctor electrode of the 20th switching tube are connected as a brachium pontis, 13rd switching tube, 15th switching tube, 17th switching tube, the colelctor electrode of the 19th switching tube is connected, 14th switching tube, sixteenmo closes pipe, eighteenmo closes pipe, the emitter stage of the 20th switching tube is connected.

The switching tube that the present invention uses is by a single-way switch pipe and a diodes in parallel composition, and time in parallel, the emitter stage of single-way switch pipe is connected with the anode of diode, and the colelctor electrode of single-way switch pipe is connected with the negative electrode of diode.

Described diode can be the anti-of IGBT diode, it is also possible to is the parasitic diode of MOSFET.

The invention also discloses the three-dimensional space vectors control method being applied to above-mentioned three-phase four-arm isolated form inverter, useForm definition on off state, wherein S_aRepresent the 13rd switching tube Q_a1, the 5th switching tube Q_a2, the 6th switching tube Q_a3, the 14th switching tube Q_a4On off state, S_bRepresent the 15th switching tube Q_b1, the 7th switching tube Q_b2, the 8th switching tube Q_b3, sixteenmo close pipe Q_b4, S_cRepresent the 17th switching tube Q_c1On off state, the 9th switching tube Q_c2, the tenth switching tube Q_c3, eighteenmo close pipe Q_c4On off state, S_nRepresent the 19th switching tube Q_n1, the 11st switching tube Q_n2, twelvemo close pipe Q_n3, the 20th switching tube Q_n4On off state；

Q_i1During conducting, S_iIt is 0⁺；Q_i2During conducting, S_iIt is 1^-；Q_i3During conducting, S_iIt is 1⁺；Q_i4During conducting, S_iIt is 0^-；Q_i2With Q_i3When being both turned on, S_iIt is 1, wherein i=a, b, c, n；S₁Represent the first switching tube Q_s1, the 4th switching tube Q_s4On off state, S₂Represent second switch pipe Q_s2, the 3rd switching tube Q_s3On off state, conducting is 1, and shutoff is 0；Sign{vTr} represents transformator both end voltage direction, and Same Name of Ends is for just representing positive direction；Space voltage vector composition three-dimensional graph synthesized by the on off state of all various combinations, forms six prisms；Three-dimensional space vectors figure projects to obtain on α β plane a hexagon, comprises 6 nonzero voltage space vectors and 2 Zero voltage vectors；These nonzero voltage space vectors and Zero voltage vector are all defined as basic voltage vectors；By 6 nonzero voltage space vector directions, whole hexagon is divided into six sectors, and in space, whole six prisms be divide into 6 triangular prisms；6 triangular prisms are carried out Further Division according to three-phase current direction, each triangular prism is divided into 2 little triangular prisms, the most whole six prisms are divided into 12 little triangular prisms, in each little triangular prism, three-phase current direction does not changes, there are three nonzero voltage space vectors and two Zero voltage vectors in each triangular prism, these basic voltage vectors effects synthesize target voltage vector；When Vector modulation, by controlling the amplitude meeting target voltage vector action time and the phase angle of each basic voltage vectors, ensure the voltage-second balance of transformator simultaneously.

Isolating transformer in three-phase four-arm isolated form inverter of the present invention has buck and electrical isolation dual-use function, the DC voltage of input is transformed to single-phase AC voltage by the inversion of inverter bridge leg, then the isolation and three-phase four-arm, diode brachium pontis and two-way switch by isolating transformer is transformed to three-phase alternating voltage.Solve the three-phase inverter of band unbalanced load in prior art to realize high frequency electrical isolation and realize the problem that the inverter of high frequency electrical isolation does not possess band unbalanced load ability at present.In addition, inverter of the present invention also has the function of buck output.

Accompanying drawing explanation

Fig. 1 is three-phase four-arm isolated form inverter circuit structural representation of the present invention.

Fig. 2 is three-phase four-arm isolated form inverter output voltage positive-sequence component of the present invention, negative sequence component and zero-sequence component extraction figure.

Fig. 3 is three-phase four-arm isolated form inverter control block diagram of the present invention.

Fig. 4 is the three dimensions voltage vector-diagram of conventional three-phase four-leg inverter.

Fig. 5 is three-phase four-arm isolated form inverter sector division figure of the present invention.

Fig. 6 is the corresponding space voltage vector figure in three-phase four-arm isolated form inverter sector 1 and 2 of the present invention.

Fig. 7 is the corresponding each switching tube drive waveforms in three-phase four-arm isolated form inverter sector 1 of the present invention.

Fig. 8 is the three-phase four-arm isolated form inverter of the present invention simulation waveform under threephase load asymmetrical.

Detailed description of the invention

Below in conjunction with the accompanying drawings 1～8 and specific embodiment, the present invention is described in further detail.

Fig. 1 is the circuit basic structure schematic diagram of described three-phase four-arm isolated form inverter, and the two-way switch group 5 that is made up of input filter capacitor 1, inverter bridge leg 2, isolating transformer 3,4, four two-way switch of diode brachium pontis, three-phase four-arm 6, output filter 7 form.Q in Fig. 1_s1、Q_s2、Q_s3、Q_s4、Q_a1、Q_a4、Q_b1、Q_b4、Q_c1、Q_c4、Q_n1、Q_n4、Q_a2、Q_a3、Q_b2、Q_b3、Q_c2、Q_c3、Q_n2、Q_n3For switching tube, D_p1、D_p2For diode, Q_s1By a single-way switch pipe and diode D_s1It is formed in parallel, Q_s2By a single-way switch pipe and diode D_s2It is formed in parallel, Q_s3By a single-way switch pipe and diode D_s3It is formed in parallel, Q_s4By a single-way switch pipe and diode D_s4It is formed in parallel, Q_a1By a single-way switch pipe and diode D_a1It is formed in parallel, Q_a4By a single-way switch pipe and diode D_a4It is formed in parallel, Q_b1By a single-way switch pipe and diode D_b1It is formed in parallel, Q_b4By a single-way switch pipe and diode D_b4It is formed in parallel, Q_c1By a single-way switch pipe and diode D_c1It is formed in parallel, Q_c4By a single-way switch pipe and diode D_c4It is formed in parallel, Q_n1By a single-way switch pipe and diode D_n1It is formed in parallel, Q_n4By a single-way switch pipe and diode D_n4It is formed in parallel, Q_a2By a single-way switch pipe and diode D_a2It is formed in parallel, Q_a3By a single-way switch pipe and diode D_a3It is formed in parallel, Q_b2By a single-way switch pipe and diode D_b2It is formed in parallel, Q_b3By a single-way switch pipe and diode D_b3It is formed in parallel, Q_c2By a single-way switch pipe and diode D_c2It is formed in parallel, Q_c3By a single-way switch pipe and diode D_c3It is formed in parallel, Q_n2By a single-way switch pipe and diode D_n2It is formed in parallel, Q_n3By a single-way switch pipe and diode D_n3Being formed in parallel, time in parallel, the emitter stage of single-way switch pipe is connected with the anode of diode, and colelctor electrode is connected with the negative electrode of diode.D_s1、D_s2、D_s3、D_s4、D_a1、D_a4、D_b1、D_b4、D_c1、D_c4、D_n1、D_n4、D_a2、D_a3、D_b2、D_b3、D_c2、D_c3、D_n2、D_n3Can be the anti-of IGBT diode, it is also possible to be the parasitic diode of MOSFET.When switching frequency is relatively low, use common commutation diode；When switching frequency is higher, use fast recovery diode or Schottky diode.

Described inverter bridge leg 2 is made up of four switching tubes, the first switching tube Q_s1Emitter stage and second switch pipe Q_s2Colelctor electrode be connected as a brachium pontis, the 3rd switching tube Q_s3Emitter stage and the 4th switching tube Q_s4Colelctor electrode be connected as a brachium pontis, the first switching tube Q_s1, the 3rd switching tube Q_s3Colelctor electrode be connected, second switch pipe Q_s2, the 4th switching tube Q_s4Emitter stage be connected.

Described diode brachium pontis 4 is made up of two diodes, the first diode D_p1Anode and the second diode D_p2Negative electrode be connected.

The two-way switch group 5 of described four two-way switch composition is made up of eight switching tubes, the 5th switching tube Q_a2Emitter stage and the 6th switching tube Q_a3Emitter stage be connected to form a two-way switch, the 7th switching tube Q_b2Emitter stage and the 8th switching tube Q_b3Emitter stage be connected to form a two-way switch, the 9th switching tube Q_c2Emitter stage and the tenth switching tube Q_c3Emitter stage be connected to form a two-way switch, the 11st switching tube Q_n2Emitter stage and twelvemo close pipe Q_n3Emitter stage be connected to form a two-way switch.

Described three-phase four-arm 6 is made up of eight switching tubes, the 13rd switching tube Q_a1Emitter stage and the 14th switching tube Q_a4Colelctor electrode be connected as a brachium pontis, the 15th switching tube Q_b1Emitter stage and sixteenmo close pipe Q_b4Colelctor electrode be connected as a brachium pontis, the 17th switching tube Q_c1Emitter stage and eighteenmo close pipe Q_c4Colelctor electrode be connected as a brachium pontis, the 19th switching tube Q_n1Emitter stage and the 20th switching tube Q_n4Colelctor electrode be connected as a brachium pontis, the 13rd switching tube Q_a1, the 15th switching tube Q_b1, the 17th switching tube Q_c1, the 19th switching tube Q_n1Colelctor electrode be connected, the 14th switching tube Q_a4, sixteenmo close pipe Q_b4, eighteenmo close pipe Q_c4, the 20th switching tube Q_n4Emitter stage be connected.

Input filter capacitor 1 (C_in) in parallel with inverter bridge leg 2, isolating transformer 3 primary side winding termination of the same name first switching tube Q_s1With second switch pipe Q_s2Series connection point, different name termination the 3rd switching tube Q_s3With the 4th switching tube Q_s4Series connection point；By in parallel with three-phase four-arm for diode brachium pontis, by the first diode D time in parallel_p1Negative electrode and the 13rd switching tube Q_a1Colelctor electrode be connected, the second diode D_p2Anode and the 14th switching tube Q_a4Emitter stage be connected；By the 5th switching tube Q_a2Colelctor electrode be connected on the 13rd switching tube Q_a1With the 14th switching tube Q_a4Series connection point, by the 7th switching tube Q_b2Colelctor electrode be connected on the 15th switching tube Q_b1Pipe Q is closed with sixteenmo_b4Series connection point, by the 9th switching tube Q_c2Colelctor electrode be connected on the 17th switching tube Q_c1Pipe Q is closed with eighteenmo_c4Series connection point, the 11st switching tube Q_n2Colelctor electrode be connected on the 19th switching tube Q_n1With the 20th switching tube Q_n4Series connection point；By the 6th switching tube Q_a3Colelctor electrode, the 8th switching tube Q_b3Colelctor electrode, the tenth switching tube Q_c3Colelctor electrode, twelvemo close pipe Q_n3Colelctor electrode be all connected on isolating transformer 3 vice-side winding Same Name of Ends, vice-side winding different name terminates at the first diode D_p1With the second diode D_p2Series connection point；By three output inductor L_a、L_b、L_cOne end respectively with three output filter capacitor C_a、C_b、C_cOne end series connection, the other end meets the 13rd switching tube Q respectively_a1With the 14th switching tube Q_a4Series connection point, the 15th switching tube Q_b1Pipe Q is closed with sixteenmo_b4Series connection point, the 17th switching tube Q_c1Pipe Q is closed with eighteenmo_c4Series connection point.Threephase load R_La、R_Lb、R_LcRespectively with three output filter capacitor C_a、C_b、C_cIn parallel.Three output filter capacitor C_a、C_b、C_cThe other end be connected, by Inductor L_nThe points of common connection (i.e. exporting ground wire) of one termination output filter capacitor, another terminates the 19th switching tube Q_n1With the 20th switching tube Q_n4Series connection point.Below as a example by the three-phase four-arm isolated form inverter in Fig. 1, describe the specific works principle of three-phase four-arm isolated form inverter respectively in conjunction with Fig. 2-7.

Before analysis, making the following assumptions: 1) all switching tubes and diode be ideal component；2) all inductance, electric capacity and transformator are ideal element.

In fig. 1, n_pFor transformer primary side umber of turn, n_sFor the vice-side winding number of turn.i_La、i_Lb、i_LcFor A, B, C three pole reactor electric current, i_oa、i_ob、i_ocFor threephase load electric current, i_nFor n phase current, u_an、u_bn、u_cnFor three-phase output voltage.In fig 2, u_{od_p}、u_{oq_p}For output voltage positive-sequence component value under the biphase rotating coordinate system of dq, u_{od_n}、u_{oq_n}For output voltage negative sequence component value under the biphase rotating coordinate system of dq, u_{od_0}For output voltage zero-sequence component.In fig. 3, u_{od_pref}、u_{oq_pref}For output voltage positive-sequence component reference value under the biphase rotating coordinate system of dq, u_{od_nref}、u_{oq_nref}For output voltage negative sequence component reference value under the biphase rotating coordinate system of dq, u_{od_0ref}For output voltage zero-sequence component reference value.i_{od_p}、i_{oq_p}For load current positive-sequence component value under the biphase rotating coordinate system of dq, i_{od_n}、i_{oq_n}For load current negative sequence component value under the biphase rotating coordinate system of dq, i_{od_0}For load current zero-sequence component.i_{Ld_p}、i_{Lq_p}For inductive current positive-sequence component value under the biphase rotating coordinate system of dq, i_{Ld_n}、i_{Lq_n}For inductive current negative sequence component value under the biphase rotating coordinate system of dq.v_{d_p}、v_{q_p}For reference voltage vector positive-sequence component value under the biphase rotating coordinate system of dq, v_{d_n}、v_{q_n}For reference voltage vector negative sequence component value under the biphase rotating coordinate system of dq.v_{α _p}、v_{β _p}For reference voltage vector positive-sequence component value under the biphase rest frame of α β, v_{α _n}、v_{β _n}For reference voltage vector negative sequence component value under the biphase rest frame of α β, v_α、v_β, v_rFor reference voltage vector value under α β γ three-dimensional system of coordinate.

Changer input side joint direct voltage source V_dc, export side joint threephase load R_La、R_Lb、R_Lc.When threephase load is asymmetric, three-phase output voltage not only comprises positive-sequence component, further comprises negative sequence component and zero-sequence component.Use symmetrical component method to decomposite the positive-sequence component of three-phase output voltage, negative sequence component and zero-sequence component, three components are respectively controlled.As shown in Figure 2, first three-phase output voltage is carried out the conversion of positive sequence Park and (value under abc three-phase static coordinate system is transformed to the value under the biphase rotating coordinate system of dq, also referred to as 3s/2r conversion), and through band elimination filter filter 2 times of fundamental frequencies component of voltage (i.e. negative sequence component positive sequence Park convert after value), then can obtain positive-sequence component value u under biphase rotating coordinate system_{od_p}, u_{oq_p}；Output voltage is carried out the conversion of negative phase-sequence Park, and filters the component of voltage (i.e. positive-sequence component value after negative phase-sequence Park converts) of 2 times of fundamental frequencies through band elimination filter, then can obtain negative sequence component value u under biphase rotating coordinate system_{od_n}, u_{oq_n}；And zero-sequence component u_{od_0}Can be calculated by three-phase output voltage and obtain.Respectively to u_{od_p}, u_{oq_p}, u_{od_n}, u_{oq_n}, u_{od_0}It is adjusted, use output voltage outer ring, the Double-loop Control Strategy of output current inner loop that changer is controlled, owing to there is certain coupling between dq axle, so using feed forward decoupling control that it is decoupled, being respectively controlled d axle and q axle component, control block diagram is as shown in Figure 3.

From the control block diagram of accompanying drawing 3 it can be seen that space vector modulation (SVPWM) algorithm is the core of control algolithm.Conventional two-dimensional space Vector Modulation can only control three brachium pontis, thus cannot be directly used to three-phase four-leg inverter.In three-phase four-leg inverter, due to band unbalanced load so that the space vector of three-phase four-leg inverter is positioned at three dimensions, therefore, in three dimensions, required target voltage vector u can be synthesized with static voltage vector with simulating two-dimensional space vector modulation_ref, except for the difference that, u_refThe track in three dimensions is become from two-dimensional space.Although this three-dimensional space vector modulation method has been applied to three-phase four-leg inverter, but is not particularly suited for three-phase four-arm isolated form inverter, because existing method does not ensures that the voltage-second balance of transformator, thus changer can not be made normally to work.Therefore for the three-phase four-arm isolated form inverter of the present invention, it is proposed that a kind of three-dimensional space vector modulation method that can apply to three-phase four-arm isolated form inverter.Correspondingly, in the space vector modulating method proposed, it is proposed that a kind of new sector partitioning method, the sector partitioning method of three-dimensional space vector modulation is simplified.

Accompanying drawing 4 is the three-dimensional space vectors figure of conventional three-phase four-leg inverter, its space voltage vector and on off state one_to_one corresponding.But three-phase four-arm isolated form inverter proposed by the invention comprises transformator, transformator both end voltage can be to be just negative, the most same space voltage vector can be realized by different on off states, and the voltage-second balance of transformator to be ensured during Vector modulation.Three-phase four-arm isolated form inverter is consistent with the three-dimensional space vectors figure of non-isolation type inverter, but on off state corresponding to sector partitioning method, vector and vector composite analysis are the most different.

1 on off state definition:

UseForm definition on off state, wherein S_a、S_b、S_c、S_nRepresent Q respectively_{a1 ~ 4}, Q_{b1 ~ 4}, Q_{c1 ~ 4}, Q_{n1 ~ 4}On off state.Q_i1During conducting, S_iIt is 0⁺；Q_i2During conducting, S_iIt is 1^-；Q_i3During conducting, S_iIt is 1⁺；Q_i4During conducting, S_iIt is 0^-；Q_i2With Q_i3When being both turned on, S_iIt is 1；Wherein i=a, b, c, n；S₁、S₂Represent Q respectively_s1,4、Q_s2,3On off state, conducting is 1, and shutoff is 0.Sign{vTr} represents transformator both end voltage direction, Same Name of Ends for just representing positive direction (+), Same Name of Ends for negative represent negative direction (-).

2 sector partitioning methods:

From the vectogram of Fig. 4 it can be seen that due to the existence of γ-value so that space vector constitutes three-dimensional graph, defines six prisms, and six prisms are divided into seven aspects according to the difference of γ-value.Three-dimensional space vectors figure projects to can obtain on α β plane a hexagon, comprises 6 nonzero voltage space vectors and 2 Zero voltage vectors.By 6 nonzero voltage space vector directions, whole hexagon can be divided into six sectors, and in space, whole six prisms be divide into 6 triangular prisms.Partitioning standards is as two-dimensional space Vector Modulation, only by three-phase voltage value v under biphase rest frame_α、v_βDetermine.From analyzing, for three-phase four-arm isolated form inverter proposed by the invention, assume three-phase output electric current and voltage in phase, then for same triangular prism, a phase current direction is wherein had to change, this is by different for the voltage vector causing same on off state to synthesize, it is thus desirable to 6 triangular prisms are carried out Further Division according to three-phase current direction, each triangular prism is divided into 2 little triangular prisms, the most whole six prisms are divided into 12 little triangular prisms, and in each little triangular prism, three-phase current direction does not changes.Therefore, on α β plane, hexagon is divided into 12 little sectors and carries out Vector modulation.In order to distinguish 12 sectors, being numbered 12 sectors is 1～12, as shown in Figure 5.Be illustrated in figure 6 the three dimensional vector diagram of the planar triangular prism of sector 1 and 2 correspondence, in each triangular prism, have three nonzero voltage space vectors and two Zero voltage vectors, these basic voltage vectors effects target voltage vector corresponding in synthesizing each triangular prism.

3 vector composite analysis:

In the triangular prism of sector 1 correspondence, target voltage vector to be synthesized can be by This basic voltage vectors synthesis corresponding to five kinds of on off states.In order to reduce switch switching times to reduce switching loss, switch switch sequence as follows:

$\begin{array}{c}\begin{array}{ccccc}{\left(0^{+}{1}^{-}{1}^{-}1\right)}_{01}^{-}& {\left(1^{+}{1}^{-}{1}^{-}1\right)}_{00}^0& {\left(1^{+}{0}^{-}{0}^{-}{0}^{-}\right)}_{10}^{+}& {\left(1^{+}{0}^{-}{0}^{-}1\right)}_{10}^{+}& \end{array},{\left(1^{+}{1}^{-}{0}^{-}1\right)}_{10}^{+}{|}_{T_s/2}\\ \begin{array}{ccccc}{\left(1^{+}{1}^{-}{0}^{-}1\right)}_{10}^{+}& {\left(1^{+}{0}^{-}{0}^{-}1\right)}_{10}^{+}& {\left(1^{+}{0}^{-}{0}^{-}{0}^{-}\right)}_{10}^{+}& {\left(1^{+}{1}^{-}{1}^{-}1\right)}_{00}^0& {\left(0^{+}{1}^{-}{1}^{-}1\right)}_{01}^{-}{|}_{T_s}\end{array}\end{array}$

And in the triangular prism of sector 2 correspondence, target voltage vector to be synthesized can be by This basic voltage vectors synthesis corresponding to five kinds of on off states, switch switch sequence is as follows:

$\begin{array}{cccccc}{\left(0^{+}{0}^{+}{1}^{-}{0}^{+}\right)}_{01}^{-}& {\left(0^{+}{0}^{+}{1}^{-}1\right)}_{01}^{-}& {\left(0^{+}{1}^{+}{1}^{-}1\right)}_{01}^{-}& {\left(1^{+}{1}^{+}{1}^{-}1\right)}_{00}^0& {\left(1^{+}{1}^{+}{0}^{-}1\right)}_{10}^{+}{|}_{T_s/2}& \\ {\left(1^{+}{1}^{+}{0}^{-}1\right)}_{10}^{+}& {\left(1^{+}{1}^{+}{1}^{-}1\right)}_{00}^0& {\left(0^{+}{1}^{+}{1}^{-}1\right)}_{01}^{-}& {\left(0^{+}{0}^{+}{1}^{-}1\right)}_{01}^{-}& {\left(0^{+}{0}^{+}{1}^{-}{0}^{+}\right)}_{01}^{-}{|}_{T_s}& \end{array}$

4 switching tube dutycycles calculate:

In order to synthesize target voltage vector, the action time of each basic voltage vectors all be there are certain requirements.The amplitude of vector to be ensured and phase angle, the voltage-second balance of transformator to be ensured during resultant vector.

In the triangular prism of sector 1 correspondence, on off stateWithCorresponding three-phase brachium pontis output voltage values is [u_an u_bn u_cn]=[V_dc0 0], total dutycycle is defined as d₁；On off stateCorresponding three-phase brachium pontis output voltage values is [u_an u_bn u_cn]=[0-V_dc -V_dc], dutycycle is defined as d₂；On off stateCorresponding three-phase brachium pontis output voltage values is [u_an u_bn u_cn]=[0 0-V_dc], dutycycle is defined as d₃；Therefore, the dutycycle of each on off state is:

$d_{{\left(0^{+}{1}^{-}{1}^{-}1\right)}_{01}^{-}}+d_{{\left(1^{+}{0}^{-}{0}^{-}{0}^{-}\right)}_{10}^{+}}=d_1;$

$d_{{\left(1^{+}{0}^{-}{0}^{-}1\right)}_{10}^{+}}=d_2;$

$d_{{\left(1^{+}{1}^{-}{0}^{-}1\right)}_{10}^{+}}=d_3;$

Assume that target voltage vector magnitude of voltage under α β γ three-dimensional system of coordinate is U_ref=[u_α u_β u_γ], Clark conversion the magnitude of voltage that the magnitude of voltage under three-phase abc coordinate system can be converted under α β γ three-dimensional system of coordinate:

$\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\\ u_{\mathrm{\γ}}\end{array}=0\begin{array}{ccc}\frac{2}{3}& -\frac{1}{3}& -\frac{1}{3}\\ 0& \frac{\sqrt{3}}{3}& -\frac{\sqrt{3}}{3}\\ \frac{1}{3}& \frac{1}{3}& \frac{1}{3}\end{array}\begin{array}{c}{u}_{\mathrm{an}}\\ u_{\mathrm{bn}}\\ u_{\mathrm{cn}}\end{array}\begin{array}{c}{d}_1{T}_s\\ d_2{T}_s\\ d_3{T}_s\end{array}=\begin{array}{ccc}\frac{2}{3}& -\frac{1}{3}& -\frac{1}{3}\\ 0& \frac{\sqrt{3}}{3}& -\frac{\sqrt{3}}{3}\\ \frac{1}{3}& \frac{1}{3}& \frac{1}{3}\end{array}\begin{array}{ccc}{V}_{\mathrm{dc}}& 0& 0\\ 0& {-V}_{\mathrm{dc}}& 0\\ 0& {-V}_{\mathrm{dc}}& {-V}_{\mathrm{dc}}\end{array}\begin{array}{c}{d}_1{T}_s\\ d_2{T}_s\\ d_3{T}_s\end{array}=\begin{array}{ccc}\frac{2}{3}& \frac{2}{3}& \frac{1}{3}\\ 0& 0& \frac{\sqrt{3}}{3}\\ \frac{1}{3}& -\frac{1}{3}& -\frac{1}{3}\end{array}\begin{array}{c}{d}_1{T}_s\\ d_2{T}_s\\ d_3{T}_s\end{array}{V}_{\mathrm{dc}}$

Wherein T_sFor switch periods.Therefore, by target voltage vector magnitude of voltage under α β γ three-dimensional system of coordinate and given input direct voltage value, d can be calculated₁、d₂、d₃Value:

$\begin{array}{c}{d}_1\\ d_2\\ d_3\end{array}=\begin{array}{cccc}& 1& 0& \frac{1}{2}\\ \frac{1}{V_{\mathrm{dc}}}& \frac{1}{2}& -\frac{\sqrt{3}}{2}& -1\\ & 0& \sqrt{3}& 0\end{array}\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\\ u_{\mathrm{\γ}}\end{array}$

Which ensure that amplitude and the phase angle of synthesized vector, but do not ensure that the voltage-second balance of transformator.So that changer normally works, need to ensure that transformator both end voltage is that the positive time is equal with the time for bearing.Therefore, the dutycycle that each on off state is corresponding also needs to meet relationship below:

$d_{{\left(0^{+}{1}^{-}{1}^{-}1\right)}_{01}^{-}}=d_{{\left(1^{+}{0}^{-}{0}^{-}{0}^{-}\right)}_{10}^{+}}+d_{{\left(1^{+}{0}^{-}{0}^{-}1\right)}_{10}^{+}}+d_{{\left(1^{+}{1}^{-}{0}^{-}1\right)}_{10}^{+}}$

Thus can be calculated the dutycycle of all on off states: $d_{{\left(1^{+}{0}^{-}{0}^{-}{0}^{-}\right)}_{10}^{+}}=\frac{d_1-d_2-d_3}{2};d_{{\left(1^{+}{0}^{-}{0}^{-}1\right)}_{10}^{+}}=d_2;d_{{\left(1^{+}{1}^{-}{0}^{-}1\right)}_{10}^{+}}=d_3;d_{{\left(1^{+}{1}^{-}{1}^{-}1\right)}_{00}^0}=1-(d_1+d_2+d_3).$

The dutycycle of each on off state is combined the drive waveforms that i.e. can get sector 1, as shown in Figure 7 with switching sequence.The drive waveforms of remaining sector in like manner can obtain, and repeats no more.

Fig. 8 is that three-phase four-arm isolated form inverter of the present invention is at the simulation waveform as a example by the asymmetric situation of a kind of threephase load.Wherein A phase load is 96.8 Europe, and B phase load is 48.4 Europe, and C phase load is 48.4 Europe.As shown in Figure 8, three-phase output voltage remains to keep balance, has reached intended technique effect.

The concrete application approach of the present invention is a lot, and the above is only the preferred embodiment of the present invention, it should be pointed out that; for those skilled in the art; under the premise without departing from the principles of the invention, it is also possible to make some improvement, these improvement also should be regarded as protection scope of the present invention.

Claims (1)

1. a three-dimensional space vectors control method for three-phase four-arm isolated form inverter, is characterized in that:

Described three-phase four-arm isolated form inverter includes: input filter capacitor (1), inverter bridge leg (2), isolating transformer (3), Diode brachium pontis (4), the two-way switch group (5) of four two-way switch compositions, three-phase four-arm (6), output filter (7)； Inverter bridge leg (2) is in parallel with input filter capacitor (1), (2) two brachium pontis midpoints of inverter bridge leg respectively with isolating transformer (3) Primary side winding two ends are connected；Diode brachium pontis (4) is in parallel with three-phase four-arm (6), in (6) four brachium pontis of three-phase four-arm Point one end with four two-way switch respectively is connected, and the other end of four two-way switch is all with isolating transformer (3) vice-side winding together Name end is connected, and diode brachium pontis (4) midpoint is connected with isolating transformer (3) vice-side winding different name end；Output filter (7) For LC wave filter, it is made up of four filter inductances and three filter capacitors；One end of four filter inductances respectively with three-phase four bridge In arm (6), the midpoint of four brachium pontis is connected, wherein the other end of three filter inductances respectively with one end of three output filter capacitors Series connection, three output filter capacitor other ends are connected, and constitute output ground；Threephase load is in parallel with three output filter capacitors respectively； Another termination output ground of 4th filter inductance；

Inverter bridge leg (2) is made up of four switching tubes, the first switching tube Q_s1Emitter stage and second switch pipe Q_s2Colelctor electrode It is connected as a brachium pontis, the 3rd switching tube Q_s3Emitter stage and the 4th switching tube Q_s4Colelctor electrode be connected as a brachium pontis, First switching tube Q_s1, the 3rd switching tube Q_s3Colelctor electrode be connected, second switch pipe Q_s2, the 4th switching tube Q_s4Emitter stage phase Even；

Two-way switch group (5) is made up of eight switching tubes, the 5th switching tube Q_a2Emitter stage and the 6th switching tube Q_a3Transmitting Pole is connected to form a two-way switch, the 7th switching tube Q_b2Emitter stage and the 8th switching tube Q_b3Emitter stage be connected to form one Two-way switch, the 9th switching tube Q_c2Emitter stage and the tenth switching tube Q_c3Emitter stage be connected to form a two-way switch, the tenth One switching tube Q_n2Emitter stage and twelvemo close pipe Q_n3Emitter stage be connected to form a two-way switch；

Three-phase four-arm (6) is made up of eight switching tubes, the 13rd switching tube Q_a1Emitter stage and the 14th switching tube Q_a4's Colelctor electrode is connected as a brachium pontis, the 15th switching tube Q_b1Emitter stage and sixteenmo close pipe Q_b4Colelctor electrode be connected conduct One brachium pontis, the 17th switching tube Q_c1Emitter stage and eighteenmo close pipe Q_c4Colelctor electrode be connected as a brachium pontis, the tenth Nine switching tube Q_n1Emitter stage and the 20th switching tube Q_n4Colelctor electrode be connected as a brachium pontis, the 13rd switching tube Q_a1、 15th switching tube Q_b1, the 17th switching tube Q_c1, the 19th switching tube Q_n1Colelctor electrode be connected, the 14th switching tube Q_a4、 Sixteenmo closes pipe Q_b4, eighteenmo close pipe Q_c4, the 20th switching tube Q_n4Emitter stage be connected；

UseForm definition on off state, wherein S_aRepresent the 13rd switching tube Q_a1, the 5th switching tube Q_a2, the 6th switching tube Q_a3, the 14th switching tube Q_a4On off state, S_bRepresent the 15th switching tube Q_b1, the 7th switching tube Q_b2, the 8th switching tube Q_b3, sixteenmo close pipe Q_b4On off state, S_cRepresent the 17th switching tube Q_c1, the 9th switching tube Q_c2, the tenth switching tube Q_c3, eighteenmo close pipe Q_c4On off state, S_nRepresent the 19th switching tube Q_n1, the 11st switch Pipe Q_n2, twelvemo close pipe Q_n3, the 20th switching tube Q_n4On off state；

Q_i1During conducting, S_iIt is 0⁺；Q_i2During conducting, S_iIt is 1^-；Q_i3During conducting, S_iIt is 1⁺；Q_i4During conducting, S_iIt is 0^-；Q_i2With Q_i3When being both turned on, S_iIt is 1, wherein i=a, b, c, n；S₁Represent the first switching tube Q_s1, the 4th switching tube Q_s4Switch shape State, S₂Represent second switch pipe Q_s2, the 3rd switching tube Q_s3On off state, conducting is 1, and shutoff is 0；Sign{v_TrRepresent Transformator both end voltage direction, Same Name of Ends is for just representing positive direction；Space voltage synthesized by the on off state of all various combinations Vector composition three-dimensional graph, forms six prisms；Three-dimensional space vectors figure projects to obtain on α β plane a hexagon, Comprise 6 nonzero voltage space vectors and 2 Zero voltage vectors；These nonzero voltage space vectors and Zero voltage vector are all defined as substantially Voltage vector；By 6 nonzero voltage space vector directions, whole hexagon is divided into six sectors, and by whole six prisms in space Divide into 6 triangular prisms；6 triangular prisms are carried out Further Division according to three-phase current direction, each triangular prism is divided into 2 little triangular prisms, the most whole six prisms are divided into 12 little triangular prisms, and in each little triangular prism, three-phase current direction does not occurs Change, has three nonzero voltage space vectors and two Zero voltage vectors in each triangular prism, these basic voltage vectors effects synthesize Target voltage vector；When Vector modulation, meet target voltage vector by controlling the action time of each basic voltage vectors Amplitude and phase angle, ensure the voltage-second balance of transformator simultaneously.