CN104753379B - Mid-point voltage adjusting method for three-phase tri-level inverter - Google Patents
Mid-point voltage adjusting method for three-phase tri-level inverter Download PDFInfo
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- CN104753379B CN104753379B CN201510170375.7A CN201510170375A CN104753379B CN 104753379 B CN104753379 B CN 104753379B CN 201510170375 A CN201510170375 A CN 201510170375A CN 104753379 B CN104753379 B CN 104753379B
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Classifications
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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
-
- 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
- H02M7/53—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 using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/539—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
- H02M7/5395—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
Abstract
The present invention relates to a kind of mid-point voltage adjusting method for three-phase tri-level inverter, according to the maximum and minimum value and the difference of DC voltage of the three-phase bridge arm voltage of three-level inverter, the numerical value that the voltage vector of the corresponding three-phase bridge arm of PWM cycle can be increased or decreased simultaneously is calculated；A mid-point voltage adjustment factor is given, to solve the control time for obtaining switching device in three-phase bridge arm；By the control time according to PWM rule and the carrier wave ratio of three-level inverter compared with and generating the control instruction to drive switching device in the three-level inverter.The present invention realizes that the regulation of alignment voltage is controlled by the selection of switching variable, it is easy to accomplish, operation efficiency can be effectively improved.
Description
Technical field
The present invention relates to field of inserter control, more particularly to a kind of mid-point voltage for controlling three-phase tri-level inverter is adjusted
Section method.
Background technology
Multi-electrical level inverter is adapted to Large Copacity, the occasion of high pressure, has obtained increasing application.Tri-level inversion utensil
There is multiple switch component, the switch combination of component is configured to the output voltage of inverter.The switch of multiple switch component
The various combination of state is set to provide the space vector of voltage of output voltage, this topological structure, each power switch pipe
The maximum voltage born is the 1/2 of DC voltage, further, since phase voltage has three kinds of level states, than two traditional level
The many level of inverter, therefore output waveform quality is high.Thus this Structural Transformation device is in high-performance, the change of high voltage appearance
Frequency modulation speed, the field such as active electric filter device and power system reactive power compensation has a wide range of applications.But, this converter
Three level are produced using two electric capacity series connection, when being changed due to the inconsistent and converter energy of switching device self character
Midpoint potential participates in the transmission of energy, therefore, the problem of producing two capacitance voltage unbalanced-voltage-divisions, i.e. neutral balance problem.
If midpoint potential is uneven, low-order harmonic can be produced in exchange outlet side, makes the delivery efficiency step-down of inverter, same to time-harmonic wave
Can also pulsating torque be produced to motor, influence the speed adjusting performance of motor；In addition, the voltage that some switching tubes of inverter are born increases
Height, reduces the reliability of system；Finally, Neutral-point Potential Fluctuation reduces the life-span of DC bus capacitor.
The content of the invention
It is an object of the invention to provide a kind of simple regulation side for easily realizing three-phase tri-level inverter neutral point voltage balance
Method, using special coordinates conversion and specific vector rule, alignment voltage is realized by the selection of switching variable
Regulation.
In order to achieve the above object, the technical scheme is that providing a kind of midpoint for three-phase tri-level inverter
Voltage adjusting method, includes procedure below：
According to the three-phase bridge arm voltage V of three-level inverterA,VB,VC, defined variable M is VA,VB,VCIn maximum with
DC voltage VdcDifference, the voltage vector of the corresponding three-phase bridge arm of PWM cycle is represented by variable MCan be same
When increased numerical value；
Defined variable N is three-phase bridge arm voltage VA,VB,VCIn minimum value and DC voltage VdcDifference, pass through variable N
Represent voltage vectorThe numerical value that can reduce simultaneously；
M=Vdc-max(VA,VB,VC)
N=Vdc-min(VA,VB,VC)
According to given mid-point voltage adjustment factor k, the control time T of switching device in three-phase bridge arm is solvedA,TB,TC,
Wherein：
When mid-point voltage need not be adjusted, k=0 is taken：
When needing to heighten mid-point voltage, k ∈ (0,1) are taken：
When needing to turn down mid-point voltage, k ∈ (- 1,0) are taken：
By the control time T tried to achieveA,TB,TC, according to the PWM rule of three-level inverter with carrier wave ratio compared with next life
Into the control instruction to drive switching device in the three-level inverter.
The voltage vector of three-phase tri-level meets following relation in three-level inverter：
Wherein,For current input reference voltage vector, TPWMIt is pulse width modulation cycle.
According to given reference voltage UrCalculating obtains the three-phase bridge arm voltage VA,VB,VC, its scope is met [- Vdc,+
Vdc]：
The present invention is asked by providing a kind of mid-point voltage adjusting method for three-level inverter to solve neutral balance
Topic.The present invention is only slightly handled the modulating wave for exporting PWM, does not influence inverter integrally to control, and Digital Implementation is simple, can have
Effect improves operation efficiency.
Brief description of the drawings
Fig. 1 is the typical circuit topological diagram of three-phase tri-level inverter of the present invention；
Fig. 2 is to illustrate k in the present invention to take (- 1,1) not influence the analysis chart of output voltage vector；
Fig. 3 is the flow chart of the neutral point voltage balance algorithm of the present invention；
PWM waveform when Fig. 4 is k=0 under certain of the invention input condition；
Fig. 5 is the PWM waveform when present invention is k=1 under input condition identical with Fig. 4；
Fig. 6 is the PWM waveform when present invention is k=-1 under input condition identical with Fig. 4.
Embodiment
Below in conjunction with the embodiment of the brief description of the drawings present invention.
Fig. 1 example provides a kind of typical circuit topological diagram of three-phase tri-level inverter, midpoint electricity of the present invention
Press adjusting method, it is adaptable to three-phase tri-level inverter and it is similar therewith there are three direct current incoming levels, export three-phase electricity
The power electronic system of pressure.
In the output relation of three-level inverter, the voltage vector of three-phase tri-level meets following relation：
Wherein,For current input reference voltage vector,For PWM (the pulsewidth tune calculated
System) cycle corresponding inverter three-phase bridge arm voltage vector.TPWMIt is pulse width modulation cycle, TA,TB,TCRespectively three-phase three is electric
The control time of flat three voltage bridge arms of inverter, the control time of the control time correspondence switching tube of bridge arm.
It is the example of voltage vector composite diagram, wherein A as shown in Figure 2, B, C is three-phase voltage reference axis, VrefIt is input
Reference voltage vector；T1, T2 lines represent one group of vector, T1 ', T3 ' lines represent another group of vector.According to plane geometry
Principle understands that the vector of the vector and T1 ' and T3 ' synthesis of T1 and T2 synthesis is all Vref.This explanation is for given reference vector
For resultant vector mode it is not unique.
I other words,The output according to vectorial combination logical constitutionAs can be seen from the figure 2,Increase or reduce identical numerical value to synthesis simultaneouslyAll it is identical.That is, for appointing
What meaning was instantaneously calculatedIncreaseing or decreasing identical numerical value simultaneously does not influence output, and still, this is simultaneously
Increase or the numerical value reduced can cause the change of mid-point voltage；Also, this numerical value for increasing or reducing simultaneously is not any
, but limited by the characteristic of inverter.
Mid-point voltage adjusting method of the present invention, its midpoint regulation logic flow chart as shown in figure 3, the present invention
Method directly increases a calculation step in original modulation system, without changing modulation system.
The computational methods of the present invention, are comprised the steps of：
Step 1, calculated according to the modulator approach of three-level inverter and obtain VA, VB, VC；
That is, according to given reference voltage UrCalculate the three-phase bridge arm voltage V for obtaining corresponding three-level inverterA, VB, VC；
Limited by the output relation of actual inverter, VA, VB, VCScope must be fulfilled for [- Vdc,+Vdc]。
Therefore, according to SPWM (sinusoidal pulse width modulation) modulation system, obtain
Step 2, two variables M, N, respectively V are definedA, VB, VCIn maximum/minimum and DC voltage Vdc's
Difference；
That is, the numerical value solved respectively by formula (4) and formula (5), asIt can increase simultaneously
Maximum M, and the minimum value N that can reduce simultaneously.
M=Vdc-max(VA,VB,VC) (4)
N=Vdc-min(VA,VB,VC) (5)
Step 3, mid-point voltage adjustment factor k, k scope (- 1,1) are defined.K-factor is by artificially giving, correspondence mid-point voltage
Three kinds of situations of regulation, work as k>0 (0,1) is needed toward positive regulator, k<0 (- 1,0) need not be adjusted toward negative regulator, k=0.K determines
The principle of justice is that its absolute value is closer to 0, and the effect of regulation is smaller, and absolute value is closer to 1, and governing speed is faster.
Step 4, controlled according to coefficient kThe numerical value that three variables are increasedd or decreased simultaneously, passes through formula
(6) the three kinds of different situations in~(8) point are handled, when solving the control of corresponding three voltage bridge arms of three-phase tri-level inverter
Between TA,TB,TC, so as to reach the purpose of control mid-point voltage.
When need not adjust：
When midpoint low voltage, it is necessary to which voltage is up adjusted：
When mid-point voltage is higher, it is necessary to which voltage is down adjusted：
TA,TB,TCPWM drivings are relatively generated with carrier wave ratio according to the modulating rule of three-level inverter.So as to according to three level
The PWM method of inverter, is generated to the control instruction for some switching devices for driving the inverter.
PWM waveform when Fig. 4 is k=0 under certain of the invention input condition, the part of its bend filling has for PWM waveform
Imitate part.As can be seen from the figure PWMA, PWMB are greater than 0, and PWMC is less than 0.
PWM waveform when Fig. 5 is k=1 (positive regulator) under identical with Fig. 4 input condition of the present invention, wherein wave point is filled
Part is the increased live part of PWM waveform institute on the basis of Fig. 4, and the part of grid filling is then the PWM on the basis of Fig. 4
The part that waveform is reduced.Waveform difference compared with Fig. 4 is that PWMA, PWMB, PWMC add M=V simultaneouslydc-max(VA,
VB,VC)。
PWM waveform when Fig. 6 is k=-1 (negative regulator) under identical with Fig. 4 input condition of the present invention, wherein wave point is filled
Part is the increased live part of PWM waveform institute on the basis of Fig. 4, and the part of grid filling is the PWM ripples on the basis of Fig. 4
The part that shape is reduced.Waveform difference compared with Fig. 4 is that PWMA, PWMB, PWMC reduce N=V simultaneouslydc-min(VA,
VB,VC)。
In summary, mid-point voltage adjusting method of the present invention, using special coordinates conversion and specific vector
Transformation law, adjusts mid-point voltage by the selection of switching variable, is adapted to three-phase tri-level inversion system.The present invention is only to defeated
The modulating wave for going out PWM is slightly handled, and does not influence inverter integrally to control, and Digital Implementation is simple, can effectively improve operation efficiency.
Although present disclosure is discussed in detail by above preferred embodiment, but it should be appreciated that above-mentioned
Description is not considered as limitation of the present invention.After those skilled in the art have read the above, for the present invention's
A variety of modifications and substitutions all will be apparent.Therefore, protection scope of the present invention should be limited to the appended claims.
Claims (3)
1. a kind of mid-point voltage adjusting method for three-phase tri-level inverter, it is characterised in that include procedure below：
According to the three-phase bridge arm voltage V of three-level inverterA,VB,VC, defined variable M is VA,VB,VCIn maximum and direct current
Side voltage VdcDifference, the voltage vector of the corresponding three-phase bridge arm of pulse width modulation cycle is represented by variable MCan
While increased numerical value；
Defined variable N is three-phase bridge arm voltage VA,VB,VCIn minimum value and DC voltage VdcDifference, represented by variable N
Voltage vectorThe numerical value that can reduce simultaneously；
M=Vdc-max(VA,VB,VC)
N=Vdc-min(VA,VB,VC)
According to given mid-point voltage adjustment factor k, the control time T of switching device in three-phase bridge arm is solvedA,TB,TC, wherein：
When mid-point voltage need not be adjusted, k=0 is taken：
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By the control time T tried to achieveA,TB,TC, according to the PWM rule of three-level inverter with carrier wave ratio compared with to generate use
To drive the control instruction of switching device in the three-level inverter.
2. mid-point voltage adjusting method as claimed in claim 1, it is characterised in that
The voltage vector of three-phase tri-level meets following relation in three-level inverter：
Wherein,For current input reference voltage vector, TPWMIt is pulse width modulation cycle.
3. mid-point voltage adjusting method as claimed in claim 1, it is characterised in that
According to given reference voltage UrCalculating obtains the three-phase bridge arm voltage VA,VB,VC, its scope is met [- Vdc,+Vdc]：
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2
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| Application Number | Priority Date | Filing Date | Title |
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| CN201510170375.7A CN104753379B (en) | 2015-04-10 | 2015-04-10 | Mid-point voltage adjusting method for three-phase tri-level inverter |
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| CN201510170375.7A CN104753379B (en) | 2015-04-10 | 2015-04-10 | Mid-point voltage adjusting method for three-phase tri-level inverter |
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| CN109510496B (en) * | 2018-12-03 | 2020-01-03 | 华中科技大学 | Neutral point voltage balance control method and system for NPC three-level inverter without electrolytic capacitor |
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| US7196919B2 (en) * | 2005-03-25 | 2007-03-27 | Tyco Electronics Power Systems, Inc. | Neutral point controller, method of controlling and rectifier system employing the controller and the method |
| JP5176710B2 (en) * | 2008-06-13 | 2013-04-03 | 株式会社安川電機 | Neutral point clamp power converter and control method thereof |
| CN103401457B (en) * | 2013-07-09 | 2015-07-01 | 西安交通大学 | Carrier wave modulation method of voltage type three-level neutral point clamped converter |
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