CN106803725A - A kind of diode clamping tri-level powder inverter common-mode voltage suppressing method - Google Patents

Abstract

A kind of common-mode voltage suppressing method suitable for diode clamping tri-level inverter, it is characterised in that positive small vector is removed in the vector that described method synthesizes output voltage, while maintaining neutral point voltage balance.Sector cell is numbered according to where inverter needs output voltage, basic space vector is selected, comprising zero vector, transition small vector, the big vector of middle vector.In order to control neutral point voltage balance, two negative small vectors with 120 degree of transition small vector mutual deviation are introduced as the first additional small vector and the second additional small vector.According to transition small vector, the first additional small vector and the corresponding three-phase current of the second additional small vector and mid-point voltage deviation, mid-point voltage control is divided into 3 kinds of operating modes, calculates the control ability of every kind of operating mode alignment voltage, control ability the maximum is optimum operating condition.Optimum operating condition according to selection calculates each vector final action time, controls power electronic devices break-make, and output common mode voltage magnitude is reduced into 1/6 DC bus-bar voltage.

Description

A kind of diode clamping tri-level powder inverter common-mode voltage suppressing method

Technical field

The present invention relates to a kind of common-mode voltage suppressing method suitable for diode clamping tri-level inverter.

Background technology

With the energy and the protrusion of environmental problem, more sight are invested regenerative resource, its apoplexy by countries in the world Power generates electricity and has become the renewable energy power generation mode of current on the largest scaleization exploit condition and commercialized development prospect.In wind , it is necessary to PWM frequency converters are processed electric energy during power generates electricity, wherein the four-quadrant being made up of diode clamping tri-level inverter Current transformer have energy conversion efficiency it is high, control the low advantages of relatively easy, du/dt be widely adopted, but applied at it There are some negative effects in journey, typical problem is the high frequency common mode voltage that inverter is produced.

High frequency common mode voltage can induce high frequency shaft voltage on alternator shaft, and then form shaft current, and corrosion generates electricity Machine bearing.High frequency common mode voltage interacts with generator windings parasitic capacitance, reduces winding insulation against ground；While high frequency common mode Voltage produces very strong electromagnetic interference, influences the normal operation of other control systems and electronic equipment.With the rising of voltage, electricity Power equipment is available for the voltage margin of design less and less, it is contemplated that many level blocks are to realize high-tension classical pathway, research Many level PWM inverter output common mode voltage suppression technologies have important theory significance and practical value.

Document《The research of common-mode voltage suppression technology in multilevel SPWM frequency converter》The such as Jiang Yanshu, Xu Dianguo,《It is more electric The suppression of flat powder inverter common-mode voltage》Zhao Li, Song Pinggang etc., propose to suppress powder inverter common-mode voltage output using software mode, But neutral-point voltage balance is not considered.And neutral point voltage balance is the base of diode clamping tri-level inverter stable operation Plinth.

The content of the invention

The purpose of the present invention is the shortcoming for overcoming existing common-mode voltage suppressing method to control neutral point voltage balance, is proposed A kind of suppressing method for reducing diode clamping tri-level inverter output common mode voltage, while common-mode voltage suppression is reached 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, midpoint electric current and corresponding phase current direction, positive small vector and negative small vector are divided into by small vector when being acted on according to small vector, Using PWM (NPSVPWM) the Vector modulation strategy without 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 that output voltage synthesis will be participated in 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 alignment voltage control Ability derives optimum operating condition selection standard, realizes that alignment voltage is effectively controlled.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 S_a、S_b、S_cRepresent each bridge arm on off state of three-level inverter respectively, 0,1,2 three states correspond to respectively bridge arm-0、Three voltage outputs.The on off state for defining three-level inverter is S_aS_bS_c, then three-level inverter have 27 switches 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, such as (12) area represents the cell of the 1st sector the 2nd.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 what length was located at small vector circle is small vector, length is located at middle vector circle It is middle vector, what length was located at big vector circle is big vector.Small vector has 1 redundant state, and zero vector has 2 redundant states. Define three-phase current I_abcWith midpoint electric current I_mTo be output as just, if correspondence midpoint electric current and phase current when small vector is acted on Direction is identical, referred to as positive small vector, and such as 100,122；When small vector is acted on correspondence midpoint electric current with phase current conversely, if claim To bear small vector, such as 011,211.

The corresponding different common-mode voltage amplitudes of different vectors | V_N0|, as shown in table 1.Wherein, U_dcIt is inverter dc bus electricity Pressure.

Table 1

Wherein, middle vector correspondence common-mode voltage amplitude | V_N0|=0, big vector correspondence common-mode voltage amplitudeJust Small vector correspondence common-mode voltage amplitudeNegative small vector correspondence common-mode voltage amplitudeZero vector 111 Correspondence common-mode voltage amplitude | V_N0|=0, zero vector 000,222 corresponding common-mode voltage amplitudesIf participating in synthesis The vector state of output voltage does not include 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, remaining 19 vector positions 19 spatialities of unique correspondence.

In order to realize the purpose of suppression 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 is used for each cell, small vector, middle vector 4 bases of big vector are born 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 by selection synthesising output voltage, asks for each vector action time.For each on off sequence, in order to Control neutral point voltage balance, the big vector of vector in preferential use；Negative small vector is used for status transition and distributes the least action time T_min, referred to as transition small vector；Zero vector is filled for remaining time.If transition small vector V_stIt is T between work_st, middle vector V_mEffect Time is T_m, big vector V_lAction time is T_l, zero vector V₀Action time is T₀, sector number is n.

Defining inverter needs output voltage U_oαβIt is U in α axles component_α, it is U in beta -axis component_βIf maximum vector length isTo each vector according to DC bus-bar voltage U_dcCarry out standardization, middle vectorBig vector

Transition small vector during 1 cell of each sectorWhen calculating each vector of the 1st cell and acting on 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), T₀It is zero vector V₀Action time, T_stIt is transition small vector V_stAction time, T_mIt is middle vector V_mAction time, T_lIt is big vector V_lAction time, n is sector number, T_minIt is the distribution of transition small vector Least action time, V_αAnd V_βRespectively inverter needs output voltage U_0αβIn α axles and beta -axis component.

Each on off sequence is used for status transition comprising a negative small vector, 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, introduce 120 degree of mutual deviation other two are negative small Vector is suitable, and one side transition small vector and the two negative small vector effects for introducing correspond to different three-phase currents respectively, The real-time control demand of mid-point voltage can be met, on the other hand ensure each bridge arm device at most action one in a PWM cycle It is secondary.Other two negative small vectors that the present invention is introduced into are referred to as the first additional small vector and the second additional small vector.Wherein, The additional small vector of vector is named as the first additional small vector in synthesizing 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 on 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 (11st) cell as an example.

(11st) cell participates in output voltage synthesis basis vector and includes big vector 200, middle vector 210, transition small vector 211 and zero vector 111.In addition, controlling needs according to mid-point voltage, 121 are introduced as the first additional small vector or 112 works are introduced Be that the second additional small vector participates in output voltage synthesis, additional small vector 121 can synthesize with big vector 200 in vector 210, it is attached Plus small vector 112 can synthesize 0.5 times big vector 200 with middle vector 210.

After introducing additional small vector, according to transition small vector V_st, the first additional small vector V_sa1With the second additional small vector V_sa2The control of alignment voltage is divided into 3 kinds of operating modes by effect correspondence midpoint current symbol and mid-point voltage adjustment direction, transition Small vector adjustment mid-point voltage correspondence operating mode 1, the first additional small vector adjustment mid-point voltage correspondence operating mode 2, second adds small arrow Amount adjustment mid-point voltage correspondence operating mode 3.Operating mode 1, operating mode 2, operating mode 3 are described in detail by taking (11st) cell as an example.

Operating mode 1：Transition small vector effect correspondence midpoint current symbol meets mid-point voltage control and requires, adjusts the small arrow of transition Amount action time control mid-point voltage.For (11st) cell, big vector 200 is identical with the phase of transition small vector 211, length phase Differ from 1 times, the corresponding midpoint electric current I of the effect of transition small vector 211_m=-I_a, 211 effects make mid-point voltage liter when A phase currents are for output Height, 211 effects reduce mid-point voltage when A phase currents are for input.The adjustment of the alignment voltage of transition small vector 211 is most direct, but It is that can only be controlled toward the direction in half primitive period.

Operating mode 2：First additional small vector effect corresponding current symbol meets mid-point voltage control and requires, increases by first and adds Small vector participates in output voltage synthesis.For (11st) cell, the corresponding midpoint electric current I of the effect of the first additional small vector 121_m=- I_b, the effect of the first additional small vector 121 raises mid-point voltage when B phase currents are for output, and first adds when B phase currents are for input The effect of small vector 121 reduces mid-point voltage.Meanwhile, vector 210 in the synthesis of 121 and 200 grade time effects reduces 210 and acts on Time, the corresponding midpoint electric current I of 210 effects_m=I_b.By increase-I_bAction time, reduce I_bAction time, realize alignment electricity Pressure dual regulation effect.

Operating mode 3：Second additional small vector effect corresponding current symbol meets mid-point voltage control and requires, increases by second and adds Small vector participates in output voltage synthesis.For (11st) cell, the corresponding midpoint electric current I of the effect of the second additional small vector 112_m=- I_c, the effect of the second additional small vector 112 raises mid-point voltage when C phase currents are for output, and second adds when C phase currents are for input The effect of small vector 112 reduces mid-point voltage.Meanwhile, 112 can synthesize 0.5 times big vector with the grade time effect of middle vector 210 200, the action time of vector 210 in increase, the corresponding midpoint electric current I of 210 effects_m=I_b.By increase-I_cAction time, increase I_b Action time realizes alignment voltage dual regulation effect.

For (11st) cell, the correspondence of operating mode 1 increases the action time of transition small vector 211, realizes A phase currents alignment electricity Pressure control action；The correspondence of operating mode 2 increases the action time of the first additional small vector 121, and the action time of vector 210, realizes B in reduction Phase current alignment voltage dual regulation is acted on；The correspondence of operating mode 3 increases the action time of the second additional small vector 112, is sweared in increase Measured for 210 action times, realize that C, B biphase current alignment voltage dual regulation are acted on.3 kinds of operating modes correspond to 3 phase currents respectively, lead to Adjustment negative small vector, middle vector action time is spent, the real-time control of three-phase current alignment voltage is realized.

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 is acted in bracket Condition.

Table 3

Cell	Transition small vector	First additional small vector	Second additional small vector	Middle vector
					11
12
					21
22
					31
32
					41
42
					51
52
					61
62

After increasing mid-point voltage control strategy, each vector action time will change on the basis of formula (1) and formula (2), Define T_sa'、T₀'、T_st'、T_m'、T_l' it is respectively additional small vector V_sa, zero vector V₀, transition small vector V_st, middle vector V_m, big arrow Amount V_lFinal action time.

When controlling mid-point voltage using transition small vector, shown in each vector final action time such as formula (3)：

During using the first additional small vector control mid-point voltage, shown in each vector final action time such as formula (4)：

During using the second additional small vector control mid-point voltage, shown in each vector final action time such as formula (5).

In formula (3), formula (4), formula (5), T_sa’、T₀’、T_st’、T_m’、T_l' be respectively consideration neutral-point voltage balance after it is attached Plus small vector V_sa, zero vector V₀, transition small vector V_st, middle vector V_m, swear V greatly_lMeasure attached during final action time, wherein operating mode 2 Plus small vector V_saThe first additional small vector V of correspondence_sa1, additional small vector V during operating mode 3_saThe second additional small vector V of correspondence_sa2；T₀、 T_st、T_m、T_lRespectively using the zero vector V being calculated by formula (1) or formula (2) before mid-point voltage control₀, transition small vector V_st, middle vector V_m, big vector V_lAction time, T_minIt it is the least action time of transition small vector distribution, K is according to midpoint electricity Pressure deviation PI closed loop regulation output quantities.

Analysis mode (3), formula (4), formula (5) are as can be seen that when the different operating modes in three kinds of operating modes of selection are acted on, each vector is made To be changed with the time, the adjustment of different resultant vectors is by taking zero vector action time T₀To realize.Operating mode 1, operating mode 2nd, operating mode 3 acts on and the holding time of zero vector is respectivelyWith K (T₀-T_min).Dan Cong Zero vector holding time angle is considered, is 2 times of operating mode 1 using the cost of operating mode 2 or the adjustment mid-point voltage of operating mode 3.Meanwhile, The control ability of small vector or middle vector alignment voltage, is directly proportional with the corresponding size of current of vector effect.

The same standard that selection optimal operating condition is analyzed by taking (11st) cell as an example.In (11st) cell, the small arrow of transition The effective object of amount, the first additional small vector and the second additional small vector corresponds to A phase currents i respectively_a, B phase currents i_bWith C phases Electric current i_c, the adjustment characteristic of alignment voltage takes relation with zero vector time when being acted on reference to different operating modes, defines different works The control ability of condition alignment voltage is e, as shown in formula (6)：

In formula (6), e₁、e₂、e₃Respectively operating mode 1, operating mode 2, the wherein control ability of the alignment voltage of operating mode 3, operating mode 1 The control ability e of alignment voltage₁2 multiplying factors are taken because operating mode 1 is operating mode 2 or operating mode 3 to zero vector holding time, The control ability e of the alignment voltage of operating mode 2₂Two electric current i of middle appearance_bBecause increasing by the first additional small vector effect during operating mode 2 B phase currents, sign (Δ U are all corresponded to vector effect in reduction_neut) it is mid-point voltage symbol.The implication of formula (6) is according in Point voltage sign and vector action characteristic obtain alignment voltage control capability e when different operating modes are acted on, and control ability e is included e₁、e₂And e₃, e₁Correspondence operating mode 1, e₂Correspondence operating mode 2, e₃Correspondence operating mode 3.Wherein control ability e the maximum alignment voltage control Ability is most strong, to adjust the optimum condition of mid-point voltage.

The present invention is comprised 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 again according to angle Point, preceding 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 U_oαβIdentification sector and cell number.Specific method：Output voltage U is needed to inverter_oαβIn α axles and Beta -axis component U_αAnd U_βAsk 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 At 70 degree, it is 2 to be rounded up divided by 60, and sector number is 2, and remainder 10 is less than 30, and cell id is 1.

Step 2：Output voltage U is needed according to inverter_oαβPlace sector cell is numbered, and selection participates in output voltage synthesis Basic space vector, described basic space vector includes zero vector V₀, transition small vector V_st, middle vector V_mWith big vector V_l。 By taking (11st) 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 inverter_oαβPlace sector cell is numbered, and is calculated according to formula (1) and formula (2) Zero vector V₀, transition small vector V_st, middle vector V_m, big vector V_lAction time, T is designated as respectively₀、T_st、T_mAnd T_l；

Step 4：In order to realize mid-point voltage U_neutBalance control, output voltage U is needed according to inverter_oαβPlace sector Cell number, will be with transition small vector V_stLocus differs 120 degree of two negative small vectors as the first additional small vector V_sa1 Small vector V additional with second_sa2.Wherein, with basis vector in big vector V_lVector V in common synthesis_mAdditional small vector life Entitled first additional small vector V_sa1, with the middle vector V in basis vector_mSynthesize 0.5 times big vector V jointly_lAdditional small vector It is named as the second additional small vector V_sa2.By taking (11st) cell as an example, 121 can synthesize with big vector 200 in vector 210, referred to as First additional small vector V_sa1, 112 can synthesize 0.5 times big vector 200, the referred to as second additional small vector V with middle vector 210_sa2。

Step 5：Output voltage U is needed according to inverter_oαβPlace sector cell is numbered, with reference to transition small vector V_st, first Additional small vector V_sa1Small vector V additional with second_sa2Corresponding three-phase current I_abcWith mid-point voltage U_neutDeviation, according to formula (6) 3 kinds of control ability e of operating mode alignment voltage are calculated, control ability e includes e₁、e₂And e₃, e₁Correspondence operating mode 1, e₂Correspondence operating mode 2, e₃Correspondence operating mode 3.Selection control ability e the maximum is optimized operation operating mode.

Step 6：According to the basic space vector that step 2 is selected, the additional small vector of step 4 selection, step 5 is selected most Excellent operating condition, each basis vector action time that step 3 is calculated, substitutes into formula (3), formula (4) or formula (5) each vector of calculating final Action time, on off sequence is generated, control correspondence power electronic devices break-make 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, realizes suppressing powder inverter common-mode voltage output on the premise of device hardware cost is not increased, and reduces common-mode voltage to other The harm of equipment.

Brief description of the drawings

Fig. 1 diode clamping tri-levels topology；

Fig. 2 three-level inverters space vector is divided；

The additional small vectors of cell of Fig. 3 (11st) and the mutual compositive relation of other vectors；

Fig. 4 diode clamping tri-levels powder inverter common-mode voltage suppresses tactful block diagram.

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 gathers positive and negative DC bus-bar voltage, remembers respectively It is U_dcPAnd U_dcN；Collection three-phase alternating current, is designated as I_abc, wherein A phase, B phase, C phase respectively correspond to I_a、I_bAnd I_c；To positive direct-current Busbar voltage U_dcPWith negative DC bus-bar voltage U_dcNSummation, obtains DC bus-bar voltage U_dc；Align busbar voltage U_dcPWith negative direct current Busbar voltage U_dcNMake the difference, obtain mid-point voltage deviation delta U_neut。

Inverter uses vector control method, and vector control module output inverter shown in 10 needs output voltage in Fig. 1 U_oαβ.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 according to this 1~6；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 whole vector space is divided into 12 cells, as shown in Figure 2.Output voltage is needed according to inverter U_oαβ, sector and cell number are recognized, as shown in Fig. 4 110.Specific method：To inverter output voltage U_oαβIn α axles and β axles Component U_αAnd U_βAsk for arc tangent and obtain vector space angle, θ, vector space angle, θ rounds up as sector number divided by 60；Together When remainder be the 1st cell less than 30 degree, remainder is more than or equal to 30 degree for the 2nd cell.For example when vector space angle, θ is 70 degree When, it is 2 to ask whole upwards, and sector number is 2, and remainder 10 is less than 30, and cell id is 1.

Step 2：Output voltage U is needed according to inverter according to 110 parts in Fig. 4_oαβThe sector cell numbering of identification, choosing The basic space vector for participating in output voltage synthesis is selected, described basic space vector includes zero vector V₀, transition small vector V_st、 Middle vector V_mWith big vector V_l, as shown in Fig. 4 120.By taking (11st) cell as an example, basic space vector comprising zero vector 111, Transition small vector 211, middle vector 210 and big vector 200；

Step 3：Output voltage U is needed according to inverter according to 110 parts in Fig. 4_oαβThe sector cell numbering of identification, will DC voltage U_dc, inverter need output voltage U_oαβBring formula (1) (2) into and calculate zero vector V₀, transition small vector V_st, middle arrow Amount V_mWith big vector V_lAction time, T is designated as respectively₀、T_st、T_mAnd T_l, as shown in Fig. 4 150；

Step 4：In order to realize mid-point voltage U_neutBalance control, output is needed according to 110 parts in Fig. 4 according to inverter Voltage U_oαβThe sector cell numbering of identification, selects the first additional small vector V_a1Small vector 2V additional with second_a2, 130 in such as Fig. 4 It is shown.Wherein, the additional small vector of vector is named as the first additional small vector in synthesizing together with the big vector in basis vector V_a1, 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 V_a2.By taking (11st) cell as an example, 121 can synthesize with big vector 200 in vector 210, the referred to as first additional small vector V_sa1, 112 Can synthesize 0.5 times big vector 200, the referred to as second additional small vector V with middle vector 210_sa2, compositive relation is as shown in Figure 3.

Step 5：Output voltage U is needed according to inverter according to 110 parts in Fig. 4_oαβThe sector cell numbering of identification, ginseng According to transition small vector V_st, the first additional small vector V_a1Small vector V additional with second_a2Corresponding three-phase current I_abcAnd mid-point voltage U_neutDeviation, 3 kinds of control ability e of operating mode alignment voltage are calculated according to formula (6), and control ability e includes e₁、e₂And e₃, e₁It is right Answer operating mode 1, e₂Correspondence operating mode 2, e₃Correspondence operating mode 3.Selection control ability e the maximum is optimized operation operating mode, such as 140 institute in Fig. 4 Show.

Step 6：According to the basis vector that 120 parts in step 2 select, the additional small arrow of 130 parts selection in step 4 Amount, the optimized operation operating mode of 140 parts selection, each basis vector action time that 150 parts calculate in step 3, band in step 5 Enter formula (3), (4) or (5) and calculate each vector final action time, produce on off sequence, control correspondence power electronic devices break-make, The contravarianter voltage output for needing is realized, as shown in Fig. 4 160.

Claims (5)

1. a kind of diode clamping tri-level powder inverter common-mode voltage suppressing method, it is characterised in that：Described method is by two poles The vector space of pipe clamped three-level inverter is divided into 6 sectors, and each sector is subdivided into 2 cells, is acted on according to small vector Shi Zhongdian electric currents and corresponding phase current direction, are divided into positive small vector and negative small vector, using without positive small vector by small vector PWM (NPSVPWM) Vector modulation strategy, positive small vector is removed in the vector of output voltage synthesis, while maintaining mid-point voltage Balance；The negative small vector that output voltage synthesis will be participated in is divided into transition small vector, the first additional small arrow according to Vector modulation relation Amount and the second additional small vector, and the control ability of alignment voltage derives that optimum operating condition is selected when being acted on according to different small vectors Standard is selected, realizes that alignment voltage is effectively controlled.

2. diode clamping tri-level powder inverter common-mode voltage suppressing method according to claim 1, it is characterised in that institute The step of stating method is as follows：

Step 1, whole 360 degree of vector spaces of diode clamping tri-level inverter is divided according to angle, every 60 degree It is a sector, is divided into 6 sectors, numbering is followed successively by 1~6；60 degree of each sector space is finely divided again according to angle, preceding 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 inverter need Want output voltage U_oαβIdentification sector and cell number, specially：Output voltage U is needed to inverter_oαβIn α axles and beta -axis component U_αAnd U_βAsk for arc tangent and obtain vector space angle, θ, vector space angle, θ rounds up as sector number divided by 60；Simultaneously Remainder is the 1st cell less than 30 degree, and remainder is the 2nd cell more than or equal to 30 degree；

Step 2, output voltage U is needed according to inverter_oαβPlace sector cell is numbered, and selection participates in the base of output voltage synthesis Plinth space vector, described basic space vector includes zero vector V₀, transition small vector V_st, middle vector V_mWith big vector V_l；

Step 3, output voltage U is needed according to inverter_oαβPlace sector cell is numbered, and calculates zero vector V₀, transition small vector V_st, middle vector V_m, big vector V_lAction time, T is designated as respectively₀、T_st、T_mAnd T_l；

Step 4, in order to realize mid-point voltage U_neutBalance control, output voltage U is needed according to inverter_oαβCompile place sector cell Number, will be with transition small vector V_stLocus differs 120 degree of two negative small vectors as the first additional small vector V_sa1With second Additional small vector V_sa2；Wherein, with basis vector in big vector V_lVector V in common synthesis_mAdditional small vector be named as One additional small vector V_sa1, with the middle vector V in basis vector_mSynthesize 0.5 times big vector V jointly_lAdditional small vector be named as Second additional small vector V_sa2；

Step 5, output voltage U is needed according to inverter_oαβPlace sector cell is numbered, with reference to transition small vector V_st, first add Small vector V_sa1Small vector V additional with second_sa2Corresponding three-phase current I_abcWith mid-point voltage U_neutDeviation, calculates 3 kinds of operating modes pair The control ability e of mid-point voltage, control ability e include e₁、e₂And e₃, wherein e₁Correspondence operating mode 1, e₂Correspondence operating mode 2, e₃Correspondence work Condition 3；Selection control ability e the maximum is optimized operation operating mode；

Step 6, according to the basic space vector that step 2 is selected, the additional small vector of step 4 selection, the optimal fortune of step 5 selection Row operating mode, each basis vector action time that step 3 is calculated, substitutes into formula (3), formula (4) or formula (5) each vector of calculating and finally acts on Time, on off sequence is generated, control correspondence power electronic devices break-make realizes that inverter required voltage is exported.

3. diode clamping tri-level powder inverter common-mode voltage suppressing method according to claim 2, it is characterised in that institute State step 3 and calculate zero vector V₀, transition small vector V_st, middle vector V_m, big vector V_lAction time carried out according to below equation：

Each vector action time is as shown in formula (1) during 1 cell of each sector：

$\left\{\begin{array}{c}{T}_{st}=T_{\min }\\ T_m=\sqrt{2}\cos \frac{(2n+1)\mathrm{\π}}{6}{U}_{\mathrm{\α}}+\sqrt{2}\sin \frac{(2n+1)\mathrm{\π}}{6}{U}_{\mathrm{\β}}\\ T_l=-\sqrt{\frac{3}{2}}\cos \frac{(n+1)\mathrm{\π}}{3}{U}_{\mathrm{\α}}-\sqrt{\frac{3}{2}}\sin \frac{(n+1)\mathrm{\π}}{3}{U}_{\mathrm{\β}}-\frac{T_{\min }}{2}\\ T_0=-\sqrt{\frac{1}{2}}\cos \frac{(2n-1)\mathrm{\π}}{6}{U}_{\mathrm{\α}}-\sqrt{\frac{1}{2}}\sin \frac{(2n-1)\mathrm{\π}}{6}{U}_{\mathrm{\β}}-\frac{T_{\min }}{2}+1\end{array}\right.---\left(1\right)$

Each vector action time is as shown in formula (2) during 2 cell of each sector：

$\left\{\begin{array}{c}{T}_{st}=T_{\min }\\ T_m=\sqrt{2}\cos \frac{(2n-3)\mathrm{\π}}{6}{U}_{\mathrm{\α}}+\sqrt{2}\sin \frac{(2n-3)\mathrm{\π}}{6}{U}_{\mathrm{\β}}\\ T_l=\sqrt{\frac{3}{2}}\cos \frac{(n+1)\mathrm{\π}}{3}{U}_{\mathrm{\α}}+\sqrt{\frac{3}{2}}\sin \frac{(n+1)\mathrm{\π}}{3}{U}_{\mathrm{\β}}-\frac{T_{\min }}{2}\\ T_0=-\sqrt{\frac{1}{2}}\cos \frac{(2n-1)\mathrm{\π}}{6}{U}_{\mathrm{\α}}-\sqrt{\frac{1}{2}}\sin \frac{(2n-1)\mathrm{\π}}{6}{U}_{\mathrm{\β}}-\frac{T_{\min }}{2}+1\end{array}\right.---\left(2\right)$

In formula, T₀It is zero vector V₀Action time, T_stIt is transition small vector V_stAction time, T_mIt is middle vector V_mEffect Time, T_lIt is big vector V_lAction time, n is sector number, T_minIt is the least action time of transition small vector distribution, V_αAnd V_β Respectively inverter needs output voltage U_0αβIn α axles and the component of β axles.

4. diode clamping tri-level powder inverter common-mode voltage suppressing method according to claim 2, it is characterised in that：Institute The step of stating 5 calculates three kinds of control ability e of operating mode alignment voltage, and control ability e includes e₁、e₂And e₃, wherein e₁Correspondence work Condition 1, e₂Correspondence operating mode 2, e₃Correspondence operating mode 3；Selection control ability e the maximum is as follows for the method for optimized operation operating mode；

According to transition small vector V_st, the first additional small vector V_sa1Small vector V additional with second_sa2Effect correspondence midpoint current symbol The control of alignment voltage is divided into 3 kinds of operating modes with mid-point voltage adjustment direction；

Operating mode 1：Transition small vector effect correspondence midpoint current symbol meets mid-point voltage control and requires, adjustment transition small vector is made Use time control mid-point voltage；

Operating mode 2：First additional small vector effect corresponding current symbol meets mid-point voltage control and requires, increases by first and adds small arrow Amount participates in output voltage synthesis；

Operating mode 3：Second additional small vector effect corresponding current symbol meets mid-point voltage control and requires, increases by second and adds small arrow Amount participates in output voltage synthesis；

The adjustment characteristic of alignment voltage takes relation with zero vector time when being acted on reference to different operating modes, defines different operating modes pair The control ability of mid-point voltage is e, as shown in formula (6)：

$\left\{\begin{array}{c}{e}_1=2(-i_a)*sign\left({\mathrm{\ΔU}}_{neut}\right)\\ e_2=(-i_b-i_b)*sign\left({\mathrm{\ΔU}}_{neut}\right)\\ e_3=(-i_c+i_b)*sign\left({\mathrm{\ΔU}}_{neut}\right)\end{array}\right.---\left(6\right)$

In formula (6), e₁、e₂、e₃Respectively operating mode 1, operating mode 2, the control ability of the alignment voltage of operating mode 3, the wherein centering of operating mode 1 The control ability e of point voltage₁2 multiplying factors are taken because operating mode 1 is operating mode 2 or operating mode 3 to zero vector holding time, operating mode 2 The control ability e of alignment voltage₂Two electric current i of middle appearance_bBecause increasing by the first additional small vector effect during operating mode 2 and subtracting Small middle vector effect all corresponds to B phase currents, sign (Δ U_neut) it is mid-point voltage symbol；The implication of formula (6) is according to midpoint electricity Pressure symbol and vector action characteristic obtain alignment voltage control capability e, wherein e when different operating modes are acted on₁Correspondence operating mode 1, e₂It is right Answer operating mode 2, e₃Correspondence operating mode 3；Control ability e the maximum alignment voltage control capabilities are most strong, for control mid-point voltage most Good operating mode.

5. diode clamping tri-level powder inverter common-mode voltage suppressing method according to claim 2, it is characterised in that：Institute The method that the step of stating 6 calculates each vector final action time is as follows：

According to the basic space vector that step 2 is selected, the additional small vector of step 4 selection, the optimized operation work of step 5 selection Condition, each basis vector action time that step 3 is calculated, substitutes into formula (3), formula (4) or formula (5), when each vector of calculating is finally acted on Between；

When controlling mid-point voltage using transition small vector, shown in each vector final action time such as formula (3)：

$\left\{\begin{array}{c}{T_{sa}}^{,}=0\\ {T_0}^{,}=T_0-\frac{1}{2}K(T_0-T_{\min })\\ {T_{st}}^{,}=T_{st}+K(T_0-T_{\min })\\ {T_m}^{,}=T_m\\ {T_l}^{,}=T_l-\frac{1}{2}K(T_0-T_{\min })\end{array}\right.---\left(3\right)$

During using the first additional small vector control mid-point voltage, shown in each vector final action time such as formula (4)：

$\left\{\begin{array}{c}{T_{sa}}^{,}=K(T_0-T_{\min })\\ {T_0}^{,}=T_0-K(T_0-T_{\min })\\ {T_{st}}^{,}=T_{st}\\ {T_m}^{,}=T_m-K(T_0-T_{\min })\\ {T_l}^{,}=T_l+K(T_0-T_{\min })\end{array}\right.---\left(4\right)$

During using the second additional small vector control mid-point voltage, shown in each vector final action time such as formula (5)：

$\left\{\begin{array}{c}{T_{sa}}^{,}=\frac{2}{3}K(T_0-T_{\min })\\ {T_0}^{,}=T_0-K(T_0-T_{\min })\\ {T_{st}}^{,}=T_{st}\\ {T_m}^{,}=T_m+\frac{2}{3}K(T_0-T_{\min })\\ {T_l}^{,}=T_s-\frac{1}{3}K(T_0-T_{\min })\end{array}\right.---\left(5\right)$

In formula (3), formula (4), formula (5), T_sa’、T₀’、T_st’、T_m’、T_l' be respectively consideration neutral-point voltage balance after add it is small Vector V_sa, zero vector V₀, transition small vector V_st, middle vector V_m, swear V greatly_lAdd small when measuring final action time, wherein operating mode 2 Vector V_saThe first additional small vector V of correspondence_sa1, additional small vector V during operating mode 3_saThe second additional small vector V of correspondence_sa2；T₀、T_st、 T_m、T_lRespectively using the zero vector V being calculated by formula (1) or formula (2) before mid-point voltage control₀, transition small vector V_st, in Vector V_m, big vector V_lAction time, T_minIt it is the least action time of transition small vector distribution, K is according to mid-point voltage deviation PI closed loops adjust output quantity.