CN108270367A - A kind of three-level current transformer neutral balance control method - Google Patents
A kind of three-level current transformer neutral balance control method Download PDFInfo
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- CN108270367A CN108270367A CN201710965083.1A CN201710965083A CN108270367A CN 108270367 A CN108270367 A CN 108270367A CN 201710965083 A CN201710965083 A CN 201710965083A CN 108270367 A CN108270367 A CN 108270367A
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- control method
- current transformer
- neutral balance
- vector
- level current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/487—Neutral point clamped inverters
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Inverter Devices (AREA)
Abstract
The invention discloses a kind of three-level structure neutral balance control methods of diode clamp.The method does not change original topological structure, original vector control method is not changed, still using the Wave method of seven sections of original swtich trains, but ignore capacitance parameter, only pass through the pressure difference to upper and lower dc bus, to be adjusted to small vector proportionality coefficient, and then play the role of control bus neutral balance.This method is not that busbar neutral balance is accurately controlled, but midpoint potential is allowed to have certain fluctuation in claimed range.The present invention does not only depend on device parameters, but also can achieve the purpose that control dc bus neutral balance.
Description
A kind of three-level current transformer neutral balance control method technical field
The present invention is applied to industrial electric transmission field, is related to the neutral balance control problem of converter system.
Background technology
Diode-clamped at present（Hereinafter referred to as NPC）Three-level current transformer topological structure starts to be applied to industrial electric biography
Dynamic field, is preferably favored in mesohigh AC Drive, flexible transmission, electric network reactive compensation and absorption.Applied to mine,
Frequency converter in terms of oil pump and gradually start extensive use applied to wind-powered electricity generation, photovoltaic and large power supply with feedback net function
NPC three-level topology structures.
But NPC three-level topologies structure there are it is intrinsic the shortcomings that, be exactly that midpoint potential is unstable.Midpoint potential is uneven
Output voltage and current harmonics can be increased.Therefore neutral-point-potential balance control problem is an especially critical subject.
Presently, there are many methods, the method for comparative maturity is by unbalance voltage, DC bus capacitor capacitance, switching tube
Switch periods and space vector angle, position, accurate to calculate the time scale for control pairs of small vector, and then control
NPC three-level current transformer DC side midpoint potentials.With current transformer long-play, the parameter of some devices can change correspondingly,
Therefore control can be caused inaccurate, it is serious to even result in disorderly closedown and damage device element.
Invention content
Do not change original topological structure, do not change original vector control method, use seven sections of original on off sequences
Wave method, the method introduced one effectively in the control aspect of neutral balance and be not limited to DC bus capacitor parameter.
The present invention uses common vector control method.
The present invention uses the Wave method and seven sections of on off sequences of space vector.
The present invention still carries out pro rate to head and the tail and intermediate two pairs of small vectors, but does not use in background above and introduce
The method accurately calculated.
The present invention ignores the effect of middle vector, and rationed method is used to small vector.
From the above it can be seen that although alignment current potential of the invention is not accurately to control, allow certain fluctuation.But
Being must be in controllable allowed band.
Method provided by the invention can not consider DC bus capacitor parameter, allow ensureing that harmonic wave of output voltage controls
Within the scope of on the basis of allow neutral balance have certain fluctuation because this method does not depend on capacitance parameter, therefore capacitance
Variation does not interfere with this control method, so can stability contorting be carried out to NPC three-level current transformers for a long time.Control is got up relatively more
Add easily.
Description of the drawings
Fig. 1 is the structure function schematic diagram of the present invention.
Fig. 2 is the schematic diagram of neutral balance.
Fig. 3 is big sector division figure.
Fig. 4 is small sector division figure.
Fig. 5 is on off sequence figure.
Specific embodiment
To make the objectives, technical solutions, and advantages of the present invention clearer, below in conjunction with the accompanying drawings with specific implementation case
The present invention will be described in detail.It should be evident that the accompanying drawings in the following description is only some embodiments of the present invention, for
For those of ordinary skill in the art, without creative efforts, other are can also be obtained according to these attached drawings
Attached drawing.
Such as Fig. 1, the three-level current transformer neutral-point potential balance control method provided according to the embodiment of the present invention includes：
Step S101 according to SVPWM methods, calculates the horizontal axis alfa values of space vector and longitudinal axis beta values, according to alfa and
Beta calculates the position of vector, and then calculates the big sector at place and small sector；Step S102, according to where space vector
Sector, can obtain hair wave used in pairs of small vector；Step S103 ignores the parameter value of DC side Support Capacitor, according to
Down Highway pressure difference on DC side is carried out pro rate to pairs of small vector, is controlled with this alignment current potential.
According to fig. 2, it can be seen that the regulation mechanism of neutral balance is exactly to adjust the size of midpoint outflow and inflow current,
And then adjust busbar voltage balance.
Neutral balance control formula be:
Because small vector is the key that adjust neutral balance, therefore the present invention ignores middle vector effect, is controlled completely with small vector.
The sector where space vector of voltage is calculated, following steps can be divided into.
Such as Fig. 3, according to horizontal axis coordinate ualfa and ordinate of orthogonal axes ubeta, the big sector where space vector of voltage can be calculated.
Such as Fig. 4, by taking the 3rd big sector as an example, space vector of voltage is mapped to the both sides of big sector equilateral triangle, and then
Calculate the small sector where space vector.
Such as Fig. 5, by off sequence by arrow logo to each small sector, voltage sky has been calculated according to above step
Between big sector where vector and small sector, by off sequence, pairs of small vector can be obtained.
With the 3rd big sector, for the small sectors of E, on off sequence ONN-PNN-PON-POO-PON-PNN-ONN,（P representatives+
1 level, N represent -1 level, and O represents 0 level）, therefore pairs of small vector can be obtained as ONN and POO.Because of ONN and POO two
Vector space positions are the same, but inflow and outflow current direction in midpoint is different, therefore just by adjusting ONN and POO proportionate relationships,
To adjust neutral balance.
The proportion adjustment of pairs of small vector according to, there are two types of modes, the first is reconnaissance control, by simulate N number of point come
It adjusts.Second method is mapped in proportion by dc bus pressure difference on the proportional control factor of pairs of small vector.
First method chooses 10 points to adjust.It is calculated according to below table, COEFFICIENT K N and pressure difference VN are by oneself basis
Actual conditions are determined（0<KN<1）：
Second method is mapped to by dc bus pressure difference in proportion on the proportional control factor of pairs of small vector.
According to the following formula, coefficient k is determined according to actual conditions, and (0<k<1,0<m1<1,0<m2<1)
△Vdc>0, ONN small vector Coefficient m 1=k △ Vdc;
△Vdc>0, POO 2=1-m1 of small vector Coefficient m;
△Vdc<0, ONN small vector Coefficient m 2=k △ Vdc;
△Vdc<0, POO 1=1-m2 of small vector Coefficient m.
Claims (6)
1. a kind of three-level current transformer neutral balance control method, which is characterized in that the present invention does not change original topological structure, no
Change original vector control method, using the Wave method of seven sections of original swtich trains, be not limited to DC bus capacitor ginseng
Number, makes dc bus midpoint be constantly in a dynamic equilibrium；In order to ignore dc bus parameter role, the present invention does not use
Accurate computational methods also ignore middle vector effect, the dynamic equilibrium at midpoint are adjusted only by pairs of small vector.
2. three-level current transformer neutral balance control method according to claim 1, it is characterised in that the method is used for two poles
Clamped type three-level current transformer is managed, using vector control method, using the Wave method of seven sections of on off sequences.
3. three-level current transformer neutral balance control method according to claim 1, which is characterized in that the present invention ignores middle arrow
The adjustment effect of amount directly carries out neutral point voltage control with small vector.
4. three-level current transformer neutral balance control method according to claim 1, which is characterized in that the present invention does not have to direct current
Side bus capacitance parameter is controlled.
5. three-level current transformer neutral balance control method according to claim 1, which is characterized in that the present invention is controlled in dynamic
In system, busbar midpoint is in homeostasis process, midpoint potential is allowed to have certain fluctuation in control range.
6. three-level current transformer neutral balance control method according to claim 1, which is characterized in that the present invention is according to direct current
Busbar pressure difference carries out pro rate to pairs of small vector, and there are two types of distribution methods, and one kind is that multiple points is taken to carry out segmentation control
System；Another kind is that Linear Mapping method is taken to obtain pairs of small vector allocation proportion.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201710965083.1A CN108270367A (en) | 2017-10-17 | 2017-10-17 | A kind of three-level current transformer neutral balance control method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710965083.1A CN108270367A (en) | 2017-10-17 | 2017-10-17 | A kind of three-level current transformer neutral balance control method |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101834443A (en) * | 2010-04-22 | 2010-09-15 | 河源市雅达电子有限公司 | Method for balancing three-level direct current midpoint voltage by using time factor |
| CN102969923A (en) * | 2012-11-27 | 2013-03-13 | 上海电气集团股份有限公司 | Neutral-point potential balance control method of three-level converter |
| CN104113225A (en) * | 2013-04-18 | 2014-10-22 | 陕西省地方电力（集团）有限公司 | SVPWM realization method for proportion-variable factor neutral-point balance control strategy |
| CN105656337A (en) * | 2015-12-25 | 2016-06-08 | 冶金自动化研究设计院 | Method for realizing point voltage balance control in large-power three-level rectifier |
-
2017
- 2017-10-17 CN CN201710965083.1A patent/CN108270367A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101834443A (en) * | 2010-04-22 | 2010-09-15 | 河源市雅达电子有限公司 | Method for balancing three-level direct current midpoint voltage by using time factor |
| CN102969923A (en) * | 2012-11-27 | 2013-03-13 | 上海电气集团股份有限公司 | Neutral-point potential balance control method of three-level converter |
| CN104113225A (en) * | 2013-04-18 | 2014-10-22 | 陕西省地方电力（集团）有限公司 | SVPWM realization method for proportion-variable factor neutral-point balance control strategy |
| CN105656337A (en) * | 2015-12-25 | 2016-06-08 | 冶金自动化研究设计院 | Method for realizing point voltage balance control in large-power three-level rectifier |
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Application publication date: 20180710 |