CN106253726B - A kind of three-level inverter direct current neutral-point voltage balance method - Google Patents
A kind of three-level inverter direct current neutral-point voltage balance method Download PDFInfo
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- CN106253726B CN106253726B CN201610630637.8A CN201610630637A CN106253726B CN 106253726 B CN106253726 B CN 106253726B CN 201610630637 A CN201610630637 A CN 201610630637A CN 106253726 B CN106253726 B CN 106253726B
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- voltage
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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
Abstract
The invention discloses a kind of three-level inverter direct current neutral-point voltage balance methods.The control method of the present invention adjusts the direct current biasing and amplitude of positive negative carrier according to the fluctuation size of mid-point voltage, to realize the balance control of midpoint potential.The control method of the present invention realizes that simply, response is rapid, does not lose DC voltage utilization rate, and still ensure that harmonic distortion does not occur in output voltage electric current in mid-point voltage imbalance, the balance control that can effectively realize midpoint potential, ensures switching device safety, reduces harmonic wave of output voltage.
Description
Technical field
The present invention relates to three level DC-AC energy converting means, and in particular to a kind of three level DC-AC energy
The control method of converting means direct current midpoint potential.
Background technology
Multi-electrical level inverter can reduce the harmonic content of output voltage, reduce the voltage stress of switching device, in high pressure
Large-power occasions are widely used.Wherein three level neutral-point-clamped type inverters are studied and are most widely used.Three electricity
The precondition that flat neutral-point-clamped type inverter can work normally is that mid-point voltage keeps balance.Mid-point voltage imbalance can be led
It causes output voltage current harmonic content to increase, if voltage fluctuation degree is violent or larger steady-state deviation occurs, bridge arm can be caused to hold
It closes tube voltage stress to increase, switching tube excessive pressure damages may be made.
When in the presence of occurring in asymmetric, control in non-ideal factor, load, there are larger harmonic wave electricity on inverter structure
When stream and negative-sequence current, it can cause three level neutral-point-clamped type inverter mid-point voltages uneven.For mid-point voltage injustice
The problem of weighing apparatus, traditional has two major classes method, SVPWM methods and SPWM methods.SVPWM methods are usually by adjusting the small arrow of redundancy
Amount realizes neutral point voltage balance, and calculating is extremely complex, and harmonic wave of output voltage can be made to increase.Traditional SPWM methods usually pass through
It injects residual voltage and realizes neutral point voltage balance, it is same to calculate complexity, and DC voltage utilization rate can be caused to reduce.
At present there is also various problems in terms of three-level inverter neutral point voltage balance, solution is not yet received in these problems
Certainly.
Invention content
The problem of in terms of for the neutral point voltage balance present in traditional three-level inverter, the present invention provides a kind of meters
Calculate simple, fast uniform three-level inverter direct current neutral-point voltage balance method.
Specifically, the present invention provides a kind of three-level inverter direct current neutral-point voltage balance method, the control
For method processed for being balanced control to the direct current mid-point voltage of three-level inverter, the three-level inverter includes direct current
Source, the clamped type bridge arm of DC side electric capacity of voltage regulation C1 and C2, A phase midpoint, the clamped type bridge arm in B phases midpoint, the clamped type bridge in C phases midpoint
The midpoint of arm, three bridge arms is both connected on the midpoint of DC side electric capacity of voltage regulation C1 and C2, and the positive ends of three bridge arms connect
It is connected to the anode of the DC power supply, negative polarity end is connected to the cathode of the DC power supply, and exchange end is respectively connected to bear
A, b, c endpoint of load, which is characterized in that
The method includes following step：
(1) standard sine modulating wave is generated；
(2) asymmetric amendment is carried out to the standard sine modulating wave；
(3) the asymmetric sinusoidal modulation wave obtained after amendment is compared with carrier wave；
(4) driving sequence is generated based on comparative result；
(5) the driving sequence is sent respectively to the switching device of three bridge arms.
Further, the step (2) includes：
(2.1) the voltage V of the DC power supply is acquireddc；
(2.2) the voltage V of both described DC side electric capacity of voltage regulation C1 and C2 are acquiredC1、VC2, and mid-point voltage is calculated
Poor Δ V=VC1-VC2；
(2.3) zero-sequence component Δ V/V is added in the standard sine modulating wavedc, obtain part and correct modulating wave Vr1-1；
(2.4) by the modulating wave Vr1-1It is multiplied by coefficient V in part more than zerodc/2Vc1, obtain part and correct modulating wave
Vr1-2；
(2.5) modulating wave V is corrected into the partr1-2It is multiplied by coefficient V in minus partdc/2Vc2,
Obtain asymmetric modulation wave Vr2, expression formula is：
Wherein, m is the modulation ratio of current modulating wave.
The advantages of control method of the present invention, is：
(1) balance that is effective and quickly realizing three-level inverter mid-point voltage；
(2) it remains to that output voltage sine degree is effectively ensured in imbalance, greatly improves output voltage and electric current is humorous
Wave content；
(3) control method realizes very simple that calculation amount is small；
(4) control method will not lose DC voltage utilization rate.
Description of the drawings
Fig. 1 is the topology diagram for the three-phase tri-level inverter that the present invention is applied to；
Fig. 2 is the comparison of control method of the present invention and traditional control method；
Fig. 3 is using the method for the present invention and not use mid-point voltage comparison of wave shape before and after the method for the present invention；
Fig. 4 is output current wave compares using the method for the present invention and before and after not using the method for the present invention.
Specific implementation mode
The invention will be further described below in conjunction with the accompanying drawings.
Fig. 1 is three-phase tri-level inverter topology figure.As shown in Figure 1, the three-phase tri-level inverter includes straight
Galvanic electricity source Vdc, DC side electric capacity of voltage regulation C1 and C2, A phase switching tubes Sa1~Sa4, A phase catching diodes Da1And Da2, B phase switching tubes
Sb1~Sb4, B phase catching diodes Db1And Db2, C phase switching tubes Sc1~Sc4, C phase catching diodes Dc1And Dc2And three intersection
Current load.A phase switching tubes Sa1~Sa4, A phase catching diodes Da1And Da2Form the clamped type bridge arm in A phases midpoint；B phase switching tubes Sb1
~Sb4, B phase catching diodes Db1And Db2Form the clamped type bridge arm in B phases midpoint；C phase switching tubes Sc1~Sc4, C phase catching diodes
Dc1And Dc2Form the clamped type bridge arm in C phases midpoint.The inverter further includes control module, and control module controls signal for generating,
To control all parts in inverter.
Fig. 2 show the comparison of control method of the present invention and traditional control method.As shown in Fig. 2, three-phase tri-level inversion
When device is modulated according to traditional SPWM modulator approaches, carrier wave VcaIt is by about the horizontal symmetrical two groups of triangular wave groups of y=0
At triangle wave amplitude is 1, and frequency is switching frequency fs.Conventional modulated wave Vr1Be about the horizontal symmetrical sine waves of y=0,
Expression formula such as (I) is shown,
Its switching tube conduction mode is carried out by following formula,
Shown in the output voltage expression formula such as formula (III) obtained by traditional modulation, vab, vbcAnd vcaIt is three-phase respectively
Inverter output line voltage, Δ V=V in formulac1-Vc2, Vc1And Vc2It is electric capacity of voltage regulation C1 and C2 both end voltage respectively, due to midpoint
The presence of Voltage unbalance causes output voltage to generate Severe distortion.
The asymmetric modulation wave Vr2It generates as steps described below,
(1) zero-sequence component is added
In conventional modulated wave Vr1On the basis of real-time zero-sequence component Δ V/V is addeddc, obtain modulating wave Vr1-1；
(2) positive half-wave adjusts
By modulating wave Vr1-1It is multiplied by coefficient V in part more than zerodc/2Vc1, obtain modulating wave Vr1-2；
(3) half-wave adjustment is born
By modulating wave Vr1-2It is multiplied by coefficient V in minus partdc/2Vc2, obtain modulating wave Vr2；
Shown in asymmetric modulation wave expression formula such as formula (IV), it is modulated according to formula (IV), works as VC1When higher, asymmetric tune
Wave V processedr2Positive half-wave part can increase, and negative half-wave part can reduce, and inverter extracts capacitance C1 energy times and increases, to main
It is dynamic to make VC1Decline, and extract the reduction of capacitance C2 energy times, to actively make VC2Rise, mid-point voltage is made to restore balance, it is similar
, work as VC2When higher, asymmetric modulation wave Vr2Negative half-wave part can increase, and positive half-wave part can reduce, and inverter extracts electricity
Hold C2 energy times to increase, to actively make VC2Decline, and extract the reduction of capacitance C1 energy times, to actively make VC1Rise,
Mid-point voltage is set to restore balance；Particularly, V shown in formula (IV)r2Expression formula always meets Vr2≤ 1, therefore to DC voltage profit
There is no any loss with rate.
Asymmetric modulation wave Vr2With carrier wave VcaIt is compared, is modulated according to public formula (II) switch tube, according to this hair
The asymmetric modulation mode of bright proposition is controlled, and shown in obtained three-phase line voltage expression formula such as formula (V), is adjusted using the present invention
After mode processed, the harmonic distortion that mid-point voltage imbalance introduces is eliminated.
Fig. 3 and Fig. 4 respectively illustrates the method for the present invention using the comparison of front and back mid-point voltage simulation waveform and output voltage
Simulation waveform compares.Simulation parameter is：Switching frequency 15kHz, alternating voltage fundamental frequency 50Hz, line voltage virtual value are
380V, DC voltage VdcFor 700V, loading as 25 Europe resistance of 4.28mH inductance, modulation ratio m is that 1, C1 and C2 is 470uF, in
Point voltage difference delta V is 100V.
From figure 3, it can be seen that when midpoint voltage difference has 100V, the control method of the present invention is put at the 0.2s moment,
Mid-point voltage is promptly restored to balance, and recovery time is only 20ms, and stable state mid-point voltage difference controls within 0.5V；From Fig. 4
As can be seen that it is 100V to keep mid-point voltage difference, apparent distortion occurs for traditional control method output load current, and of the invention
Control method can ensure the very excellent sine degree of output load current.
The present invention is not only limited to above-mentioned specific implementation mode, and persons skilled in the art are according to embodiment and attached drawing public affairs
Open content, other a variety of specific implementation modes may be used and implement the present invention, therefore, every design structure using the present invention and
Thinking does some simple designs converted or change, both falls within the scope of protection of the invention.
Claims (1)
1. a kind of three-level inverter direct current neutral-point voltage balance method, the control method is used for three-level inverter
Direct current mid-point voltage be balanced control, the three-level inverter include DC power supply, DC side electric capacity of voltage regulation C1 and C2,
The clamped type bridge arm in A phases midpoint, the clamped type bridge arm in B phases midpoint, the clamped type bridge arm in C phases midpoint, the midpoint of three bridge arms is both connected to
On the midpoint of DC side electric capacity of voltage regulation C1 and C2, the positive ends of three bridge arms are connected to the anode of the DC power supply, bear
Polar end is connected to the cathode of the DC power supply, and exchange end is respectively connected to a, b, c endpoint of load, which is characterized in that
The method includes following step：
(1) standard sine modulating wave is generated；
(2) asymmetric amendment is carried out to the standard sine modulating wave；
(3) the asymmetric sinusoidal modulation wave obtained after amendment is compared with carrier wave；
(4) driving sequence is generated based on comparative result；
(5) the driving sequence is sent respectively to the switching device of three bridge arms
Wherein, the step (2) includes：
(2.1) the voltage V of the DC power supply is acquireddc；
(2.2) the voltage V of both described DC side electric capacity of voltage regulation C1 and C2 are acquiredC1、VC2, and mid-point voltage difference Δ V is calculated
=VC1-VC2；
(2.3) zero-sequence component Δ V/V is added in the standard sine modulating wavedc, obtain part and correct modulating wave Vr1-1；
(2.4) by the modulating wave Vr1-1It is multiplied by coefficient V in part more than zerodc/2Vc1, obtain part and correct modulating wave Vr1-2；
(2.5) modulating wave V is corrected into the partr1-2It is multiplied by coefficient V in minus partdc/2Vc2,
Obtain asymmetric modulation wave Vr2, expression formula is：
Wherein, m is the modulation ratio of current modulating wave.
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| CN106787889B (en) * | 2016-12-31 | 2019-05-31 | 浙江工业大学 | Three-level inverter midpoint potential feedback based on the modulation of double modulation wave carrier signal |
| CN112104247A (en) * | 2020-09-08 | 2020-12-18 | 沈阳工业大学 | Neutral-point potential control method for medium-voltage three-level full-power converter of wind generating set |
| CN114977861A (en) * | 2022-07-29 | 2022-08-30 | 深圳市首航新能源股份有限公司 | Bus voltage compensation method, electronic equipment and system thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103401456A (en) * | 2013-07-09 | 2013-11-20 | 西安交通大学 | Dual-modulating wave dual-carrier modulation method for voltage type three-level neutral point clamped converter |
| CN103401457A (en) * | 2013-07-09 | 2013-11-20 | 西安交通大学 | Carrier wave modulation method of voltage type three-level neutral point clamped converter |
| CN105226982A (en) * | 2015-11-02 | 2016-01-06 | 南京航空航天大学 | A kind of three level NPC inverter midpoint potential balance control method based on mid point electric current |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103401456A (en) * | 2013-07-09 | 2013-11-20 | 西安交通大学 | Dual-modulating wave dual-carrier modulation method for voltage type three-level neutral point clamped converter |
| CN103401457A (en) * | 2013-07-09 | 2013-11-20 | 西安交通大学 | Carrier wave modulation method of voltage type three-level neutral point clamped converter |
| CN105226982A (en) * | 2015-11-02 | 2016-01-06 | 南京航空航天大学 | A kind of three level NPC inverter midpoint potential balance control method based on mid point electric current |
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