Content of the invention
The purpose of the present invention is the shortcoming overcoming existing common-mode voltage suppressing method can not control neutral point voltage balance, proposes
A kind of suppressing method reducing diode clamping tri-level inverter output common mode voltage, while reaching common-mode voltage suppression
Neutral point voltage balance can be controlled.
The vector space of diode clamping tri-level inverter is divided into 6 sectors by the present invention, and each sector is subdivided into 2
Cell, when being acted on according to small vector, midpoint electric current and corresponding phase current direction, small vector is divided into positive small vector and negative small vector,
Using PWM (NPSVPWM) the Vector modulation strategy without positive small vector, in the vector of output voltage synthesis, remove just little arrow
Amount, maintains neutral point voltage balance simultaneously;The negative small vector participating in output voltage synthesis is divided into transition according to Vector modulation relation
Small vector, the first additional small vector and the second additional small vector, and when being acted on according to different small vectors centering point voltage control
Ability derives optimum operating condition selection standard, realizes centering point voltage effective control.The present invention can be by inverter output common mode electricity
Pressure amplitude value is reduced to 1/6 DC bus-bar voltage by 1/3 original DC bus-bar voltage.
For diode clamping tri-level inverter, it is made up of 12 IGBT and 6 clamp diodes.Use switching variable
Sa、Sb、ScRepresent three-level inverter each brachium pontis on off state respectively, 0,1,2 three states correspond to brachium pontis respectively Three voltage outputs.The on off state defining three-level inverter is SaSbSc, then three-level inverter have 27
On off state, corresponds to 19 spatialities respectively.
Whole vector space is divided into 6 sectors, each sector is divided into 2 cells, is represented with (xy), x represents sector number,
Y represents cell id, and such as (12) area represents the 1st sector the 2nd cell.Vector is divided into 4 classes according to length:Zero vector, small vector, in
The big vector of vector, is zero vector positioned at 0 point, and length is small vector positioned at small vector circle, and length is located at middle vector circle
For middle vector, length is big vector positioned at big vector circle.Small vector has 1 redundant state, and zero vector has 2 redundant states.
Define three-phase current IabcWith midpoint electric current ImAll to be just output as, if corresponding midpoint electric current and phase current during small vector effect
Direction is identical, referred to as positive small vector, and such as 100,122;If corresponding midpoint electric current is contrary with phase current during small vector effect, claim
For bearing small vector, such as 011,211.
Different vectors corresponding difference common-mode voltage amplitude | VN0|, as shown in table 1.Wherein, UdcFor inverter dc bus electricity
Pressure.
Table 1
Wherein, middle vector corresponds to common-mode voltage amplitude | VN0|=0, big vector corresponds to common-mode voltage amplitudeJust
Small vector corresponds to common-mode voltage amplitudeNegative small vector corresponds to common-mode voltage amplitudeZero vector 111
Corresponding common-mode voltage amplitude | VN0|=0, zero vector 000,222 corresponds to common-mode voltage amplitudeIf participating in synthesis
The vector state of output voltage does not comprise 000,222 two zero vectors, and inverter output common mode voltage magnitude will be fromReduce
ArriveIf removing positive small vector again, inverter output common mode voltage magnitude will be fromIt is reduced toRemoval 000,
222 two zero vectors, remove 6 positive small vectors, and remaining 19 vector positions uniquely correspond to 19 spatialities.
In order to realize the purpose of suppression common mode voltage output, the vector participating in output voltage synthesis removes two zero vectors
000 and 222, remove 6 positive small vectors.Zero vector 111, negative small vector, 4 bases of the big vector of middle vector are adopted for each cell
Plinth vector participates in output voltage synthesis.The basis vector that each cell participates in output voltage synthesis is as shown in table 2.
Table 2
Select the vector used by synthesising output voltage, ask for each vector action time.For each on off sequence, in order to
Control neutral point voltage balance, the big vector of vector in preferentially adopting;Negative small vector is used for status transition and distributes the least action time
Tmin, referred to as transition small vector;Zero vector is used for filling remaining time.If transition small vector VstIt is T between workst, middle vector VmEffect
Time is Tm, big vector VlAction time is Tl, zero vector V0Action time is T0, sector number is n.
Defining inverter needs output voltage UoαβIt is U in α axle componentα, it is U in beta -axis componentβIf maximum vector length isTo each vector according to DC bus-bar voltage UdcCarry out standardization, middle vectorBig vector
Transition small vector during 1 cell of each sectorWhen calculating the effect of the 1st cell each vector
Between as shown in formula (1).
During 2 cell of each sector, small vectorCalculate the 2nd cell each vector action time such as formula
(2) shown in.
In formula (1) and formula (2), T0For zero vector V0Action time, TstFor transition small vector VstAction time,
TmFor middle vector VmAction time, TlFor big vector VlAction time, n be sector number, TminFor the distribution of transition small vector
The least action time, VαAnd VβBeing respectively inverter needs output voltage U0αβIn α axle and beta -axis component.
Each on off sequence comprises a negative small vector for status transition, and single negative small vector cumulative function will make midpoint
Voltage loses unbalance it is necessary to introduce other negative small vectors as additional small vector, the other two introducing 120 degree of mutual deviation is negative little
Vector is suitable, and one side transition small vector and the two negative small vector effects introducing correspond to different three-phase currents respectively,
Can meet the real-time control demand of mid-point voltage, on the other hand ensure the most action one of each brachium pontis device in a PWM cycle
Secondary.Two negative small vectors of other that the present invention is introduced into are referred to as the first additional small vector and the second additional small vector.Wherein,
In synthesizing together with big vector, the additional small vector of vector is named as the first additional small vector, synthesizes 0.5 times together with middle vector
The additional small vector of big vector is named as the second additional small vector.
The present invention is with regard to transition small vector, the first additional small vector, the definition of the second additional small vector and alignment electricity
The control action of pressure, taking (11st) cell is as a example described in detail.
(11st) cell participates in output voltage synthesis basis vector and comprises big vector 200, middle vector 210, transition small vector
211 and zero vector 111.In addition, needs are controlled according to mid-point voltage, introduce 121 as the first additional small vector or introduce 112 works
Participate in output voltage synthesis for the second additional small vector, additional small vector 121 can synthesize with big vector 200 in vector 210, attached
Plus small vector 112 can synthesize 0.5 times of big vector 200 with middle vector 210.
After introducing additional small vector, according to transition small vector Vst, the first additional small vector Vsa1With the second additional small vector
Vsa2The control of centering point voltage is divided into 3 kinds of operating modes by the corresponding midpoint current symbol of effect and mid-point voltage adjustment direction, transition
Small vector adjustment mid-point voltage corresponds to operating mode 1, and the first additional small vector adjustment mid-point voltage corresponds to operating mode 2, and second adds little arrow
Amount adjustment mid-point voltage corresponds to operating mode 3.Taking (11st) cell as a example operating mode 1, operating mode 2, operating mode 3 are described in detail.
Operating mode 1:Transition small vector effect corresponding midpoint current symbol meets mid-point voltage and controls requirement, adjusts the little arrow of transition
Amount controls mid-point voltage action time.For (11st) cell, big vector 200 is identical with transition small vector 211 phase place, length phase
Differ from 1 times, the corresponding midpoint electric current I of transition small vector 211 effectm=-Ia, A phase current is that during output, 211 effects make mid-point voltage liter
Height, A phase current is that during input, 211 effects make mid-point voltage reduce.Transition small vector 211 alignment Voltage Cortrol is the most direct, but
It is can only to control toward the direction in half primitive period.
Operating mode 2:First additional small vector effect corresponding current symbol meets mid-point voltage and controls requirement, increases by first and adds
Small vector participates in output voltage synthesis.For (11st) cell, the first additional small vector 121 effect corresponds to midpoint electric current Im=-
Ib, B phase current is that during output, the first additional small vector 121 effect makes mid-point voltage raise, and B phase current adds for during input first
Small vector 121 effect makes mid-point voltage reduce.Meanwhile, vector 210 in the time effect synthesis such as 121 and 200, reduces by 210 effects
Time, the corresponding midpoint electric current I of 210 effectsm=Ib.By increase-IbAction time, reduce IbAction time, realize alignment electricity
Pressure dual regulation effect.
Operating mode 3:Second additional small vector effect corresponding current symbol meets mid-point voltage and controls requirement, increases by second and adds
Small vector participates in output voltage synthesis.For (11st) cell, the second additional small vector 112 effect corresponds to midpoint electric current Im=-
Ic, C phase current is that during output, the second additional small vector 112 effect makes mid-point voltage raise, and C phase current adds for during input second
Small vector 112 effect makes mid-point voltage reduce.Meanwhile, 112 can synthesize 0.5 times of big vector with middle vector 210 grade time effect
200, vector 210 action time in increase, the corresponding midpoint electric current I of 210 effectsm=Ib.By increase-IcAction time, increase Ib
Realize centering point voltage dual regulation effect action time.
For (11st) cell, operating mode 1 is corresponding to increase transition small vector 211 action time, realizes A phase current alignment electricity
Pressure control action;Operating mode 2 is corresponding to increase by first additional small vector 121 action time, and in minimizing, vector 210 action time, realizes B
Phase current centering point voltage dual regulation acts on;Operating mode 3 is corresponding to increase by second additional small vector 112 action time, swears in increase
Measured for 210 action times, realize the effect of C, B biphase current centering point voltage dual regulation.3 kinds of operating modes correspond to 3 phase currents respectively, lead to
Spend the negative small vector of adjustment, middle vector action time, realize the real-time control of three-phase current centering point voltage.
The rest may be inferred for other cells, summarizes as shown in table 3, electric current corresponding midpoint electric current feelings when acting on for vector in bracket
Condition.
Table 3
Cell |
Transition small vector |
First additional small vector |
Second additional small vector |
Middle vector |
11 |
211(-Ia) |
121(-Ib) |
112(-Ic) |
210(Ib) |
12 |
110(-Ic) |
101(-Ib) |
011(-Ia) |
210(Ib) |
21 |
110(-Ic) |
011(-Ia) |
101(-Ib) |
120(Ia) |
22 |
121(-Ib) |
211(-Ia) |
112(-Ic) |
120(Ia) |
31 |
121(-Ib) |
112(-Ic) |
211(-Ia) |
021(Ic) |
32 |
011(-Ia) |
110(-Ic) |
101(-Ib) |
021(Ic) |
41 |
011(-Ia) |
101(-Ib) |
110(-Ic) |
012(Ib) |
42 |
112(-Ic) |
121(-Ib) |
211(-Ia) |
012(Ib) |
51 |
112(-Ic) |
211(-Ia) |
121(-Ib) |
102(Ia) |
52 |
101(-Ib) |
011(-Ia) |
110(-Ic) |
102(Ia) |
61 |
101(-Ib) |
110(-Ic) |
011(-Ia) |
201(Ic) |
62 |
211(-Ia) |
112(-Ic) |
121(-Ib) |
201(Ic) |
After increasing mid-point voltage control strategy, each vector will change action time on the basis of formula (1) and formula (2),
Define Tsa'、T0'、Tst'、Tm'、Tl' it is respectively additional small vector Vsa, zero vector V0, transition small vector Vst, middle vector Vm, big swear
Amount VlFinal action time.
When controlling mid-point voltage using transition small vector, each vector final action time is as shown in formula (3):
When controlling mid-point voltage using the first additional small vector, each vector final action time is as shown in formula (4):
When controlling mid-point voltage using the second additional small vector, each vector final action time is as shown in formula (5).
In formula (3), formula (4), formula (5), Tsa’、T0’、Tst’、Tm’、Tl' be respectively consider neutral-point voltage balance after attached
Plus small vector Vsa, zero vector V0, transition small vector Vst, middle vector Vm, greatly swear VlMeasure attached during final action time, wherein operating mode 2
Plus small vector VsaCorresponding first additional small vector Vsa1, additional small vector V during operating mode 3saCorresponding second additional small vector Vsa2;T0、
Tst、Tm、TlIt is respectively before adopting mid-point voltage to control by formula (1) or the calculated zero vector V of formula (2)0, transition small vector
Vst, middle vector Vm, big vector VlAction time, TminThe least action time distributed for transition small vector, K is according to midpoint electricity
Pressure deviation PI closed loop adjusts output.
Analysis mode (3), formula (4), formula (5) are as can be seen that when selecting the different operating mode effect in three kinds of operating modes, each vector is made
To be changed with the time, the adjustment of different resultant vectors is passed through to take zero vector T action time0To realize.Operating mode 1, operating mode
2nd, operating mode 3 acts on the holding time to zero vector and is respectivelyWith K (T0-Tmin).Dan Cong
Zero vector holding time angle is considered, is 2 times of operating mode 1 using the cost that operating mode 2 or operating mode 3 adjust mid-point voltage.Meanwhile,
Small vector or the control ability of middle vector centering point voltage, act on corresponding size of current with vector and are directly proportional.
The standard of same taking (11st) cell as a example analysis selection optimal operating condition.In (11st) cell, the little arrow of transition
The effective object of amount, the first additional small vector and the second additional small vector corresponds to A phase current i respectivelya, B phase current ibWith C phase
Electric current ic, when acting in conjunction with different operating modes, the adjustment characteristic of centering point voltage and zero vector time take relation, the different work of definition
The control ability of condition centering point voltage is e, as shown in formula (6):
In formula (6), e1、e2、e3It is respectively operating mode 1, operating mode 2, the control ability of operating mode 3 centering point voltage, wherein operating mode 1
Control ability e of centering point voltage12 multiplying factors are taken to be because that operating mode 1 is operating mode 2 or operating mode 3 to zero vector holding time
Control ability e of operating mode 2 centering point voltage2Two electric current i of middle appearancebIt is because during operating mode 2 increasing by the first additional small vector effect
All correspond to B phase current, sign (Δ U with vector effect in reductionneut) it is mid-point voltage symbol.The implication of formula (6) is in basis
Point voltage symbol and vector action characteristic obtain alignment voltage control capability e during different operating mode effect, and control ability e comprises
e1、e2And e3, e1Corresponding operating mode 1, e2Corresponding operating mode 2, e3Corresponding operating mode 3.Wherein control ability e the maximum centering point voltage controls
Ability is the strongest, for adjusting the optimum condition of mid-point voltage.
The present invention comprises the following steps that:
Step 1:Whole 360 degree of vector spaces of diode clamping tri-level inverter are divided according to angle, often
60 degree is a sector, is divided into 6 sectors, and numbering is followed successively by 1~6;60 degree of each sector space is carried out carefully according to angle again
Point, front 30 degree of spaces are the 1st cell, and 30 degree of spaces are the 2nd cell afterwards.Whole vector space is divided into 12 cells.According to inverse
Becoming device needs output voltage UoαβIdentification sector and cell number.Concrete grammar:Inverter is needed with output voltage UoαβIn α axle and
Beta -axis component UαAnd UβAsk for arc tangent and obtain vector space angle, θ, vector space angle, θ rounds up as sector divided by 60
Number;Remainder is the 1st cell less than 30 degree simultaneously, and remainder is the 2nd cell more than or equal to 30 degree.For example when vector space angle, θ is
When 70 degree, round up as 2 divided by 60, sector number is 2, and remainder 10 is less than 30, cell id is 1.
Step 2:Output voltage U is needed according to inverteroαβPlace sector cell is numbered, and selects to participate in output voltage synthesis
Basic space vector, described basic space vector comprises zero vector V0, transition small vector Vst, middle vector VmWith big vector Vl.
Taking (11st) cell as a example, basic space vector comprises zero vector 111, transition small vector 211, middle vector 210 and big vector
200;
Step 3:Output voltage U is needed according to inverteroαβPlace sector cell is numbered, and is calculated according to formula (1) and formula (2)
Zero vector V0, transition small vector Vst, middle vector Vm, big vector VlAction time, be designated as T respectively0、Tst、TmAnd Tl;
Step 4:In order to realize mid-point voltage UneutBalance controls, and needs output voltage U according to inverteroαβPlace sector
Cell number, will be with transition small vector VstLocus differ 120 degree of two negative small vectors as the first additional small vector Vsa1
Small vector V additional with secondsa2.Wherein, with basis vector in big vector VlVector V in common synthesismAdditional small vector life
Entitled first additional small vector Vsa1, with the middle vector V in basis vectormJointly synthesize 0.5 times of big vector VlAdditional small vector
It is named as the second additional small vector Vsa2.Taking (11st) cell as a example, 121 with big vector 200 can synthesize in vector 210, referred to as
First additional small vector Vsa1, 112 can synthesize 0.5 times of big vector 200, the referred to as second additional small vector V with middle vector 210sa2.
Step 5:Output voltage U is needed according to inverteroαβPlace sector cell is numbered, with reference to transition small vector Vst, first
Additional small vector Vsa1Small vector V additional with secondsa2Corresponding three-phase current IabcWith mid-point voltage UneutDeviation, according to formula (6)
Calculate control ability e of 3 kinds of operating mode centering point voltages, control ability e comprises e1、e2And e3, e1Corresponding operating mode 1, e2Corresponding operating mode
2, e3Corresponding operating mode 3.Selection control ability e the maximum is optimized operation operating mode.
Step 6:The basic space vector being selected according to step 2, the additional small vector that step 4 selects, step 5 selects
Excellent operating condition, each basis vector action time that step 3 calculates, substituting into formula (3), formula (4) or formula (5), to calculate each vector final
Action time, generate on off sequence, control corresponding power electronic devices break-make, realize final voltage and control.
It is an advantage of the current invention that by the way of software optimization output voltage blended space vector action time, by two poles
Pipe clamped three-level inverter output common mode voltage magnitude is reduced to 1/6 dc bus electricity by 1/3 original DC bus-bar voltage
Pressure, realizes suppression powder inverter common-mode voltage output on the premise of not increasing device hardware cost, reduces common-mode voltage to other
The harm of equipment.
Specific embodiment
Further illustrate the present invention below in conjunction with the drawings and specific embodiments.
Diode clamping tri-level inverter topology is as shown in Figure 1.Inverter gathers positive and negative DC bus-bar voltage, remembers respectively
For UdcPAnd UdcN;Collection three-phase alternating current, is designated as Iabc, wherein A phase, B phase, C phase corresponding I respectivelya、IbAnd Ic;To positive direct-current
Busbar voltage UdcPWith negative DC bus-bar voltage UdcNSummation, obtains DC bus-bar voltage Udc;Align busbar voltage UdcPWith negative direct current
Busbar voltage UdcNMake the difference, obtain mid-point voltage deviation delta Uneut.
Inverter adopts vector control method, and in Fig. 1, vector control module output inverter shown in 10 needs output voltage
Uoαβ.The present invention is as shown in Figure 4 for diode clamping tri-level powder inverter common-mode voltage suppressing method:
Step 1:By whole vector space, 360 degree are divided according to angle, and every 60 degree is a sector, is divided into 6
Sector, numbering is 1~6 according to this;60 degree of each sector space is finely divided according to angle again, and front 30 degree of spaces are the 1st cell, after
30 degree of spaces are the 2nd cell, and whole vector space is divided into 12 cells, as shown in Figure 2.Output voltage is needed according to inverter
Uoαβ, identify sector and cell number, as shown in Fig. 4 110.Concrete grammar:To inverter output voltage UoαβIn α axle and β axle
Component UαAnd UβAsk for arc tangent and obtain vector space angle, θ, vector space angle, θ rounds up as sector number divided by 60;With
When remainder be the 1st cell less than 30 degree, remainder is the 2nd cell more than or equal to 30 degree.For example when vector space angle, θ is 70 degree
When, asking whole upwards is 2, and sector number is 2, and remainder 10 is less than 30, and cell id is 1.
Step 2:According to 110 parts in Fig. 4, output voltage U is needed according to inverteroαβThe sector cell numbering of identification, choosing
Select the basic space vector participating in output voltage synthesis, described basic space vector comprises zero vector V0, transition small vector Vst、
Middle vector VmWith big vector Vl, as shown in Fig. 4 120.Taking (11st) cell as a example, basic space vector comprise zero vector 111,
Transition small vector 211, middle vector 210 and big vector 200;
Step 3:According to 110 parts in Fig. 4, output voltage U is needed according to inverteroαβThe sector cell numbering of identification, will
DC voltage Udc, inverter need output voltage UoαβBring formula (1) (2) into and calculate zero vector V0, transition small vector Vst, middle arrow
Amount VmWith big vector VlAction time, it is designated as T respectively0、Tst、TmAnd Tl, as shown in Fig. 4 150;
Step 4:In order to realize mid-point voltage UneutBalance controls, and needs to export according to inverter according to 110 parts in Fig. 4
Voltage UoαβThe sector cell numbering of identification, selects the first additional small vector Va1Small vector 2V additional with seconda2, 130 in such as Fig. 4
Shown.Wherein, in synthesizing together with the big vector in basis vector, the additional small vector of vector is named as the first additional small vector
Va1, the additional small vector synthesizing 0.5 times of big vector together with the middle vector in basis vector is named as the second additional small vector
Va2.Taking (11st) cell as a example, 121 with big vector 200 can synthesize in vector 210, the referred to as first additional small vector Vsa1, 112
0.5 times of big vector 200, the referred to as second additional small vector V can be synthesized with middle vector 210sa2, compositive relation is as shown in Figure 3.
Step 5:According to 110 parts in Fig. 4, output voltage U is needed according to inverteroαβThe sector cell numbering of identification, ginseng
According to transition small vector Vst, the first additional small vector Va1Small vector V additional with seconda2Corresponding three-phase current IabcAnd mid-point voltage
UneutDeviation, calculates control ability e of 3 kinds of operating mode centering point voltages according to formula (6), and control ability e comprises e1、e2And e3, e1Right
Answer operating mode 1, e2Corresponding operating mode 2, e3Corresponding operating mode 3.Selection control ability e the maximum is optimized operation operating mode, as 140 institute in Fig. 4
Show.
Step 6:The basis vector being selected according to 120 parts in step 2, the additional little arrow that in step 4,130 parts select
Amount, the optimized operation operating mode that in step 5,140 parts select, each basis vector action time that in step 3,150 parts calculate, band
Enter formula (3), (4) or (5) and calculate each vector final action time, produce on off sequence, control corresponding power electronic devices break-make,
Realize the contravarianter voltage output needing, as shown in Fig. 4 160.