Summary of the invention
The purpose of the present invention is overcoming existing common-mode voltage suppressing method not can control neutral point voltage balance, propose
A kind of suppressing method reducing diode clamping tri-level inverter output common mode voltage, while reaching common-mode voltage inhibition
It can control neutral point voltage balance.
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, midpoint electric current and corresponding phase current direction when being acted on according to small vector, is divided into positive small vector and negative small vector for small vector,
Using PWM (NPSVPWM) the Vector modulation strategy for being free of positive small vector, just small arrow is removed in the vector of output voltage synthesis
Amount, while maintaining neutral point voltage balance;The negative small vector for participating in output voltage synthesis is divided into transition according to Vector modulation relationship
Small vector, the first additional small vector and the second additional small vector, and according to the control of alignment voltage when the effect of different small vectors
Ability derives optimum operating condition selection criteria, realizes that alignment voltage effectively controls.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 of 12 IGBT and 6 clamp diodes.Use switching variable
Sa、Sb、ScEach bridge arm switch state of three-level inverter is respectively indicated, 0,1,2 three state respectively corresponds bridge arm0、Three voltage outputs.The switch state for defining three-level inverter is SaSbSc, then three-level inverter shares 27 switches
State respectively corresponds 19 spatialities.
Entire vector space is divided into 6 sectors, each sector is divided into 2 cells, is indicated with (xy), and x represents sector number,
Y represents cell id, for example (12) area indicates the 2nd cell of the 1st sector.Vector is divided into 4 classes according to length: zero vector, small vector, in
The big vector of vector sum is zero vector positioned at 0 point, and it is small vector that length, which is located at small vector circle, and length is located at middle vector circle
For middle vector, it is big vector that length, which is located 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 ImIt is positive with output, if small vector corresponds to midpoint electric current and phase current when acting on
Direction is identical, referred to as positive small vector, and such as 100,122;If small vector effect when correspond to midpoint electric current with phase current on the contrary, if claim
Be negative small vector, and such as 011,211.
Different vectors correspond to different common-mode voltage amplitudes | 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, the corresponding common-mode voltage amplitude of zero vector 000,222If participating in synthesis
The vector state of output voltage does not include 000,222 two zero vector, and inverter output common mode voltage magnitude will be fromIt reduces
It arrivesIf 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 for inhibiting common-mode voltage output, the vector for participating in output voltage synthesis removes two zero vectors
000 and 222, remove 6 positive small vectors.Zero vector 111, negative small vector, middle vector sum 4 bases of big vector are used 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
Vector used in synthesising output voltage is selected, each vector action time is sought.For each on off sequence, in order to
Control neutral point voltage balance, the big vector of vector sum in preferential use;Negative small vector distributes the least action time for status transition
Tmin, referred to as transition small vector;Zero vector is filled for 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 n.
It defines inverter and needs output voltage UoαβIt is U in α axis componentα, it is U in beta -axis componentβIf maximum vector length isTo each vector according to DC bus-bar voltage UdcIt carries out marking change, middle vectorBig vector
Transition small vector when 1 cell of each sectorWhen calculating each vector effect of the 1st cell
Between as shown in formula (1).
When 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 is sector number, TminFor the distribution of transition small vector
Least action time, VαAnd VβRespectively inverter needs output voltage U0αβIn α axis and beta -axis component.
Each on off sequence includes that a negative small vector is used 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, other two of 120 degree of mutual deviation of introducing bear small
Vector is that suitably, one side transition small vector and the two negative small vectors effects introduced respectively correspond different three-phase currents,
It can satisfy the real-time control demand of mid-point voltage, on the other hand guarantee that each bridge arm device at most acts one in a PWM cycle
It is secondary.Other two negative small vectors of introducing are referred to as the first additional small vector and the second additional small vector by the present invention.Wherein,
The additional small vector of vector is named as the first additional small vector in synthesis together with big vector, and 0.5 times is synthesized together with middle vector
The additional small vector of big vector is named as the second additional small vector.
The present invention is about transition small vector, the first additional small vector, the definition of the second additional small vector and alignment electricity
The control action of pressure, is described in detail by taking (11) cell as an example.
It includes big vector 200, middle vector 210, transition small vector that (11) cell, which participates in output voltage synthesis basis vector,
211 and zero vector 111.In addition, controlling needs according to mid-point voltage, introducing 121 as the first additional small vector or introducing 112 works
Participate in output voltage synthesis for the second additional small vector, additional small vector 121 and big vector 200 can synthesize in vector 210, it is attached
Add small vector 112 and middle vector 210 that can synthesize 0.5 times big vector 200.
After introducing additional small vector, according to transition small vector Vst, the first additional small vector Vsa1With the second additional small vector
Vsa2It acts on corresponding midpoint current symbol and mid-point voltage adjustment direction and the control of alignment voltage is divided into 3 kinds of operating conditions, transition is small
Vector adjustment mid-point voltage corresponds to operating condition 1, and the first additional small vector adjustment mid-point voltage corresponds to operating condition 2, the second additional small vector
Adjustment mid-point voltage corresponds to operating condition 3.Operating condition 1, operating condition 2, operating condition 3 are described in detail by taking (11) cell as an example.
Operating condition 1: transition small vector acts on corresponding midpoint current symbol and meets mid-point voltage control requirement, adjusts the small arrow of transition
Measure action time control mid-point voltage.For (11) cell, big vector 200 is identical as 211 phase of transition small vector, length phase
Poor 1 times, transition small vector 211 acts on corresponding midpoint electric current Im=-Ia, 211 effects make mid-point voltage liter when A phase current is output
Height, 211 effects reduce mid-point voltage when A phase current is input.The adjustment of 211 alignment voltage of transition small vector is most direct, but
It is that can only be controlled toward the direction in half of primitive period.
The additional small vector of operating condition 2: the first effect corresponding current symbol meets mid-point voltage control and requires, and it is additional to increase by first
Small vector participates in output voltage synthesis.For (11) cell, the first additional small vector 121 acts on corresponding midpoint electric current Im=-
Ib, first adds the effect of small vector 121 and increases mid-point voltage when B phase current is output, and first is additional when B phase current is input
The effect of small vector 121 reduces mid-point voltage.Meanwhile 121 synthesize with 200 equal time effects in vector 210, reduce 210 and act on
Time, 210 act on corresponding midpoint electric current Im=Ib.Pass through increase-IbAction time reduces IbAction time realizes alignment electricity
Press dual regulation effect.
The additional small vector of operating condition 3: the second effect corresponding current symbol meets mid-point voltage control and requires, and it is additional to increase by second
Small vector participates in output voltage synthesis.For (11) cell, the second additional small vector 112 acts on corresponding midpoint electric current Im=-
Ic, second adds the effect of small vector 112 and increases mid-point voltage when C phase current is output, and second is additional when C phase current is input
The effect of small vector 112 reduces mid-point voltage.Meanwhile the time effects such as 112 and middle vector 210 can synthesize 0.5 times of big vector
200,210 action time of vector in increase, 210 act on corresponding midpoint electric current Im=Ib.Pass through increase-IcAction time increases Ib
Action time realizes alignment voltage dual regulation effect.
For (11) cell, operating condition 1 is corresponding to increase by 211 action time of transition small vector, realizes A phase current alignment electricity
Press control action;Operating condition 2 is corresponding to increase by the first additional 121 action time of small vector, and 210 action time of vector in reduction realizes B
The effect of phase current alignment voltage dual regulation;Operating condition 3 is corresponding to increase by the second additional 112 action time of small vector, swears in increase
It measured for 210 action times, realizes the effect of C, B biphase current alignment voltage dual regulation.3 kinds of operating conditions respectively correspond 3 phase currents, lead to
It crosses and adjusts negative small vector, middle vector action time, realize the real-time control of three-phase current alignment voltage.
The rest may be inferred for other cells, summarizes as shown in table 3, and electric current is corresponding midpoint electric current feelings when vector acts 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 action time will change 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 arrow
Measure VlFinal action time.
When controlling mid-point voltage using transition small vector, each vector final action time is as shown in formula (3):
When using the first additional small vector control mid-point voltage, each vector final action time is as shown in formula (4):
When using the second additional small vector control mid-point voltage, each vector final action time is as shown in formula (5).
Formula (3), formula (4), in formula (5), Tsa′、T0′、Tst′、Tm′、Tl' it is respectively attached after considering neutral-point voltage balance
Add small vector Vsa, zero vector V0, transition small vector Vst, middle vector Vm, greatly swear VlFinal action time is measured, it is wherein attached when operating condition 2
Add small vector VsaCorresponding first additional small vector Vsa1, additional small vector V when operating condition 3saCorresponding second additional small vector Vsa2;T0、
Tst、Tm、TlRespectively using the zero vector V being calculated before mid-point voltage control by formula (1) or formula (2)0, transition small vector
Vst, middle vector Vm, big vector VlAction time, TminFor the least action time of transition small vector distribution, K is according to midpoint electricity
Deviation PI closed loop is pressed to adjust output quantity.
As can be seen that when the different operating conditions in three kinds of operating conditions of selection act on, each vector is made for analysis mode (3), formula (4), formula (5)
It will be changed with the time, the adjustment of different resultant vectors is by occupying zero vector action time T0To realize.Operating condition 1, operating condition
2, operating condition 3 is acted on is respectively to the holding time of zero vectorK(T0-Tmin) and K (T0-Tmin).List is to zero
Vector holding time angle considers, is 2 times of operating condition 1 using the cost that operating condition 2 or operating condition 3 adjust mid-point voltage.Meanwhile small arrow
It is directly proportional to act on corresponding size of current to vector for the control ability of amount or middle vector alignment voltage.
The standard of analysis selection optimal operating condition equally by taking (11) cell as an example.In (11) cell, the small arrow of transition
The effective object of amount, the first additional small vector and the second additional small vector respectively corresponds as A phase current ia, B phase current ibWith C phase
Electric current ic, the adjustment characteristic of alignment voltage and zero vector time occupy relationship when in conjunction with the effect of different operating conditions, define different works
The control ability of condition alignment voltage is e, as shown in formula (6):
In formula (6), e1、e2、e3Respectively operating condition 1, operating condition 2, the control ability of 3 alignment voltage of operating condition, wherein operating condition 1
The control ability e of alignment voltage1Taking 2 multiplying factors because of operating condition 1 is operating condition 2 or operating condition 3 to zero vector holding time
The control ability e of 2 alignment voltage of operating condition2Two electric current i of middle appearancebIncrease by the first additional small vector effect when being because of operating condition 2
B phase current, sign (Δ U are all corresponded to vector effect in reductionneut) it is mid-point voltage symbol.The meaning of formula (6) is in
Point voltage sign and vector action characteristic obtain alignment voltage control capability e when the effect of different operating conditions, and control ability e includes
e1、e2And e3, e1Corresponding operating condition 1, e2Corresponding operating condition 2, e3Corresponding operating condition 3.Wherein control ability e the maximum alignment voltage controls
Ability is most strong, for the optimum condition for adjusting mid-point voltage.
Specific step is as follows by the present invention:
Step 1: entire 360 degree of vector spaces of diode clamping tri-level inverter being divided according to angle, often
60 degree are a sector, are divided into 6 sectors, and number is followed successively by 1~6;60 degree of each sector space carries out carefully again according to angle
Point, preceding 30 degree of spaces are the 1st cell, and rear 30 degree of spaces are the 2nd cell.Entire vector space is divided into 12 cells.According to inverse
Become device and needs output voltage UoαβIdentify sector and cell number.Specific method: output voltage U is needed to inverteroαβIn α axis and
Beta -axis component UαAnd UβIt seeks arc tangent and obtains vector space angle, θ, vector space angle, θ rounds up divided by 60 as sector
Number;Remainder is the 1st cell less than 30 degree simultaneously, and it is the 2nd cell that remainder, which is more than or equal to 30 degree,.Such as when vector space angle, θ is
At 70 degree, rounding up divided by 60 is 2, and sector number 2, remainder 10 is less than 30, cell id 1.
Step 2: output voltage U is needed according to inverteroαβPlace sector cell number, selection participate in output voltage synthesis
Basic space vector, the basic space vector include zero vector V0, transition small vector Vst, middle vector VmWith big vector Vl。
By taking (11) cell as an example, basic space vector includes 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 number, calculates according to formula (1) and formula (2)
Zero vector V0, transition small vector Vst, middle vector Vm, big vector VlAction time, be denoted as T respectively0、Tst、TmAnd Tl;
Step 4: in order to realize mid-point voltage UneutBalance control, needs output voltage U according to inverteroαβPlace sector
Cell number, will be with transition small vector VstSpatial position differs 120 degree of two negative small vectors as the first additional small vector Vsa1
With the second additional small vector Vsa2.Wherein, with the big vector V in basis vectorlVector V in common synthesismAdditional small vector life
Entitled first additional small vector Vsa1, with the middle vector V in basis vectormCommon synthesis vector V 0.5 times biglAdditional small vector
It is named as the second additional small vector Vsa2.By taking (11) cell as an 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 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 number, referring to transition small vector Vst, first
Additional small vector Vsa1With the second additional small vector Vsa2Corresponding three-phase current IabcWith mid-point voltage UneutDeviation, according to formula (6)
The control ability e of 3 kinds of operating condition alignment voltage is calculated, control ability e includes e1、e2And e3, e1Corresponding operating condition 1, e2Corresponding operating condition
2, e3Corresponding operating condition 3.Select control ability e the maximum for optimized operation operating condition.
Step 6: the basic space vector selected according to step 2, the additional small vector that step 4 selects, step 5 select most
Excellent operating condition, each basis vector action time that step 3 calculates, it is final to substitute into formula (3), formula (4) or each vector of formula (5) calculating
Action time generates on off sequence, controls corresponding power electronic devices on-off, realizes final voltage control.
The advantage of the invention is 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 is realized under the premise of not increasing device hardware cost and inhibits powder inverter common-mode voltage output, reduces common-mode voltage to other
The harm of equipment.
Specific embodiment
The present invention is further illustrated below in conjunction with the drawings and specific embodiments.
Diode clamping tri-level inverter topology is as shown in Figure 1.Inverter acquires positive and negative direct current busbar voltage, remembers respectively
For UdcPAnd UdcN;Three-phase alternating current is acquired, I is denoted asabc, wherein A phase, B phase, C phase respectively corresponds Ia、IbAnd Ic;To positive direct-current
Busbar voltage UdcPWith negative DC bus-bar voltage UdcNSummation, obtains DC bus-bar voltage Udc;To positive pole line voltage UdcPWith negative direct current
Busbar voltage UdcNIt makes the difference, obtains mid-point voltage deviation delta Uneut。
Inverter uses vector control method, 10 in Fig. 1 shown in vector control module output inverter need 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: entire vector space being divided for 360 degree according to angle, every 60 degree are a sector, are divided into 6
Sector, number are 1~6 according to this;60 degree of each sector space is finely divided again according to angle, and preceding 30 degree of spaces are the 1st cell, after
30 degree of spaces are the 2nd cell, and entire vector space is divided into 12 cells, as shown in Figure 2.Output voltage is needed according to inverter
Uoαβ, sector and cell number are identified, as shown in 110 in Fig. 4.Specific method: to inverter output voltage UoαβIn α axis and β axis
Component UαAnd UβIt seeks arc tangent and obtains vector space angle, θ, vector space angle, θ rounds up divided by 60 as sector number;Together
When remainder less than 30 degree be the 1st cell, remainder be more than or equal to 30 degree be the 2nd cell.Such as when vector space angle, θ is 70 degree
When, asking whole upwards is 2, sector number 2, and remainder 10 is less than 30, cell id 1.
Step 2: output voltage U being needed according to inverter according to 110 parts in Fig. 4oαβThe sector cell of identification is numbered, choosing
The basic space vector for participating in output voltage synthesis is selected, the basic space vector includes zero vector V0, transition small vector Vst、
Middle vector VmWith big vector Vl, as shown in 120 in Fig. 4.By taking (11) cell as an example, basic space vector include zero vector 111,
Transition small vector 211, middle vector 210 and big vector 200;
Step 3: output voltage U being needed according to inverter according to 110 parts in Fig. 4oαβThe sector cell of identification is numbered, will
DC voltage Udc, inverter need output voltage UoαβIt brings formula (1) (2) into and calculates zero vector V0, transition small vector Vst, middle arrow
Measure VmWith big vector VlAction time is denoted as T respectively0、Tst、TmAnd Tl, as shown in 150 in Fig. 4;
Step 4: in order to realize mid-point voltage UneutBalance control, needs to export according to 110 parts in Fig. 4 according to inverter
Voltage UoαβThe sector cell of identification is numbered, and the first additional small vector V is selecteda1With the second additional small vector 2Va2, as 130 in Fig. 4
It is shown.Wherein, the additional small vector of vector is named as the first additional small vector in synthesis together with the big vector in basis vector
Va1, the additional small vector that 0.5 times big vector is synthesized together with the middle vector in basis vector is named as the second additional small vector
Va2.By taking (11) cell as an example, 121 with big vector 200 can synthesize in vector 210, the referred to as first additional small vector Vsa1, 112
0.5 times 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: output voltage U being needed according to inverter according to 110 parts in Fig. 4oαβThe sector cell of identification is numbered, ginseng
According to transition small vector Vst, the first additional small vector Va1With the second additional small vector Va2Corresponding three-phase current IabcAnd mid-point voltage
UneutDeviation, the control ability e of 3 kinds of operating condition alignment voltage is calculated according to formula (6), and control ability e includes e1、e2And e3, e1It is right
Answer operating condition 1, e2Corresponding operating condition 2, e3Corresponding operating condition 3.Select control ability e the maximum for optimized operation operating condition, such as 140 institute in Fig. 4
Show.
Step 6: according to the basis vector of 120 parts selection in step 2, the selection of 130 parts adds small arrow in step 4
It measures, the optimized operation operating condition of 140 parts selection in step 5, each basis vector action time that 150 parts calculate in step 3, band
Enter formula (3), (4) or (5) and calculate each vector final action time, produce on off sequence, controls corresponding power electronic devices on-off,
The contravarianter voltage output needed is realized, as shown in 160 in Fig. 4.