CN108879757A - A kind of circulation inhibition method of three-phase inverter in sagging control process - Google Patents
A kind of circulation inhibition method of three-phase inverter in sagging control process Download PDFInfo
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- CN108879757A CN108879757A CN201810622245.6A CN201810622245A CN108879757A CN 108879757 A CN108879757 A CN 108879757A CN 201810622245 A CN201810622245 A CN 201810622245A CN 108879757 A CN108879757 A CN 108879757A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
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Abstract
The present invention relates to a kind of circulation inhibition method of three-phase inverter in sagging control process, circulation inhibition method when taking sagging control to carry out parallel running the present invention relates to three-phase inverter.Include the following steps：(1) according to the difference of used sagging governing equation, equivalent impedance difference type required for determining；(2) inhibition of the realization to circulation so that the equivalent resistance difference or equivalent reactance poor (3) that inverter loop current is zero are introduced into the equivalent impedance difference that inverter loop current is zero in system as virtual impedance is found out according to the relationship of equivalent impedance difference and circulation.The present invention solves the problems, such as that traditional introducing virtual impedance method inhibition inverter parallel circulation process middle impedance is difficult to measure and rejection ability is limited, realizes and adjusts virtual impedance in real time, the inhibition of circulation can be realized for different operating conditions.
Description
Technical field
The present invention relates to power-converting device and distributed electrical source domain, especially a kind of three-phase inverter is in parallel running
Circulation inhibition method in the process.
Background technique
Multiple distributed generation resources are generally comprised in micro-capacitance sensor, and the spatial distribution of distributed generation resource has dispersibility, it is each inverse
It is usually inconsistent to the line impedance loaded to become device, leads between each inverter that there are circulation, so that each inverter output power
Distribution is uneven.When circulation is serious, inverter current-limiting protection is resulted even in, it is out of service, and then cause chain reaction, so want
Ask inverter parallel system that there is good stream effect.
Sagging control controls inverter by the frequency and amplitude droop characteristic of simulation synchronous generator external characteristics
System, and can realize " plug and play " of inverter, more meet the demand of micro-capacitance sensor.But when using sagging control strategy, it is
Having differences property of line impedance in system, when shunt chopper is to line impedance difference between points of common connection, inverter
Output power cannot effectively divide equally, make between inverter that there are circulation, and due to the non-intellectual of line impedance, line impedance
Difference is usually unpredictable, increases the inhibition difficulty of circulation.
Conventional method is usually to inhibit circulation, the virtual resistance of introducing by introducing equal virtual impedance to each inverter
Anti- bigger, circulation is smaller.But consider the factors such as the fundamental wave pressure drop on virtual impedance and harmonic wave when with nonlinear load, virtually
The value of impedance should not be too large.So when practical application, the method for introducing virtual impedance is limited for the rejection ability of circulation.
Summary of the invention
For the above-mentioned prior art, the technical problem to be solved in the present invention is to provide one kind to be able to solve sagging control process
Middle traditional virtual impedance controlled the three-phase inverter of circulation rejection ability finiteness problem in inverter parallel sagging
Circulation inhibition method in journey.
In order to solve the above technical problems, a kind of loop current suppression side of the three-phase inverter of the present invention in sagging control process
Method includes the following steps：
Step 1：According to used sagging governing equation, equivalent impedance required for determining is poor：When using P-f, Q-Uo
Sagging governing equation when, it is poor that there are equivalent resistances, so that inverter loop current is zero when stable state；When using P-Uo, Q-f it is sagging
When governing equation, it is poor that there are equivalent reactances, so that inverter loop current is zero when stable state；
Step 2：Found out according to the relationship of equivalent impedance difference and circulation so that inverter loop current be zero equivalent resistance difference or
Person's equivalent reactance is poor；
Step 3：It is introduced into the equivalent impedance difference that inverter loop current is zero in system as virtual impedance, realizes
Inhibition to circulation.
A kind of circulation inhibition method of the three-phase inverter of the present invention in sagging control process further include：
1. the relationship of equivalent resistance difference and circulation in step 1 can be used following equation group to indicate：
The relationship of equivalent reactance difference and circulation in the step 1 can be used following equation group to indicate
In above-mentioned two groups of equations, R1-R2It is poor for equivalent resistance, X1-X2It is poor for equivalent reactance, wherein α1Indicate inverter 1
Output electric current is ahead of the phase of load current, α2Indicate that inverter 2 exports the phase that electric current lags behind load current, θLIt is negative
Impedance angle is carried,For each inverter output current,For load current.
2. the inverter equivalent resistance difference or equivalent reactance difference that make that circulation is zero in step 2 are to obtain in the following way
?：
The phase of output electric current and load current is obtained by using phaselocked loop, the difference of the two phase is as adjuster
Input follows load current phase by the output current phase of adjuster control inverter, and the output of adjuster is required
Equivalent impedance is poor.
3.WithFor the electric current fundamental component after bandpass filter extracts, wherein used by bandpass filter
Transmission function be：
Wherein, ωfFor the centre frequency of bandpass filter.
Beneficial effects of the present invention：It solves during traditional introducing virtual impedance method inhibits inverter parallel circulation
Lead to the problem for inhibiting circulation ability limited since impedance is difficult to measure, realizes and adjust virtual impedance in real time, can be directed to
Different operating conditions realize the inhibition of circulation.
Detailed description of the invention
Fig. 1 is using P-f, Q-UoSagging governing equation when inverter output current and load current phasor diagram.
Fig. 2 is that inverter equivalent resistance difference influences circulation.
Fig. 3 is using P-Uo, Q-f sagging governing equation when inverter output current and load current phasor diagram.
Fig. 4 is that the virtual resistance that makes circulation be zero in example is poor.
Fig. 5 is the relationship of equivalent resistance difference and inverter output current and load current phase difference, figure chain lines, dotted line
With solid line be respectively load impedance angle be 0 °, 15 ° and 30 ° when curve.
Fig. 6 is the structural block diagram of three-phase digital phaselocked loop.
Fig. 7 is the control block diagram for inhibiting inverter loop current using equivalent impedance difference.
Fig. 8 is not export electric current and circulation waveform using the inverter A phase of sharing control.
Fig. 9 is to export electric current and circulation waveform using the inverter A phase after sharing control.
Specific embodiment
The invention will be further described with reference to the accompanying drawings and examples.The embodiment of description herein is intended merely to pair
The present invention explains, rather than limitation of the invention.
The present invention has circulation rejection ability in inverter parallel for traditional virtual impedance in sagging control process
The problem of limit, impedance can be adjusted in real time to inhibit the method for circulation by providing one kind.It is mentioned by using a kind of bandpass filter
The fundamental component in output electric current and load current is taken, the phase of output electric current and load current is then obtained using phaselocked loop,
Input of the difference of the two phase as adjuster, the equivalent impedance that the output of adjuster is as required is poor, and will be above-mentioned equivalent
Impedance contrast is introduced into system as virtual impedance, realizes the inhibition to circulation.
Specifically, the parameter in the present embodiment is as follows：
Inverter output voltage amplitude given value is 40V, and frequency given value is 50Hz, switching frequency 5kHz, filtered electrical
Holding is 28.3uF, filter inductance 5.8mH, and undamped oscillation frequency is 393Hz, and load is 40 Ω resistance.Two inverters
And electromechanical sense is 1.9mH, seals in the cement resistor that resistance value is 1 Ω to inverter 1, there are two inverter equivalent impedances poor
It is different.
Step 1：According to the difference of used sagging governing equation, equivalent impedance required for determining is poor.
Using P-f, Q-UoSagging governing equation when, it is assumed that inverter 1 exports electric current and is ahead of inverter 2 and exports electricity
Stream, each inverter output currentAnd load currentRelationship is as shown in Figure 1.At this point, can be by ring by mathematical derivation
Flow table is shown as
In X1=0.6 Ω, X2Under conditions of=0.5 Ω, equivalent resistance difference R1-R2With load impedance angle θLWhen taking different value,
Circulation Δ IoContour map as shown in fig. 2, it can be seen that work as load impedance angle θLWhen variation, there is always a R1-R2So that
Circulation is zero.Similarly, work as X1And X2When for other values, a R is equally existed1-R2So that circulation is zero.
When using P-Uo, Q-f sagging governing equation when, each inverter output currentAnd load currentRelationship
As shown in Figure 3.Circulation at this time is represented by
Similar, for arbitrary R1 and R2, as load impedance angle θLWhen variation, there is always an X2-X1So that circulation is
Zero.
Step 2：It finds out so that inverter equivalent resistance difference or equivalent reactance that inverter loop current is zero are poor.
The control of inverter is using P-f, Q-U in this exampleoSagging governing equation, therefore need find so that circulation
The equivalent resistance for being zero is poor.If equivalent reactance X2=kX1, then as k and load impedance angle θLWhen variation, so that circulation Δ Io=0
Equivalent resistance difference R1-R2, as shown in Figure 4.As can be seen that working as k and load impedance angle θLWhen variation, equal existence anduniquess it is equivalent
Resistance official post circulation is zero.In view of equivalent impedance is generally difficult to measure, and also suffer from the factors such as temperature influence and
Variation, therefore accurately cannot inhibit circulation by way of precalculating virtual impedance, so it is next to need to find a kind of method
Virtual impedance is adjusted, in real time to realize the inhibition of circulation for different operating conditions.The phase of inverter output current and load current
Existence function relationship between difference and substitutional connection impedance, in different loads impedance angle, approximately linear relationship therebetween, such as
Shown in Fig. 5, and when the phase difference of inverter output current and load current is zero, corresponding equivalent resistance difference is to make ring
The equivalent resistance difference that stream is zero.Therefore, the output electric current and load current that inverter is acquired by sample circuit, via band logical
Filter obtains the fundamental component of output electric current and load current, and digital phase-locked loop shown in fig. 6 is recycled to obtain output electric current
Output current phase is set to follow load current phase, pi regulator output by pi regulator with the phase information of load current
As virtual resistance
Step 3：Virtual resistance ring is constituted according to the virtual impedance addition manner of attached drawing 7, changes the output resistance of inverter
It is anti-, and then the equivalent resistance for changing two inverters is poor, the final inhibition for realizing circulation.According to the comparison of Fig. 8 and Fig. 9 it is found that
When not using sharing control strategy, there are circulation between two inverters, circulation amplitude is about 0.167A, is using the present invention
After the circulation strategy based on equivalent impedance difference proposed, circulation amplitude is reduced to 0.04A or less, it is seen that circulation has obtained effective suppression
System.
The specific embodiment of the invention further includes：
A kind of circulation inhibition method of three-phase inverter in sagging control process, includes the following steps：
Step 1：According to the difference of used sagging governing equation, equivalent impedance required for determining is poor：When using P-
f、Q-UoSagging governing equation when, it is poor that there are equivalent resistances, so that inverter loop current is zero when stable state；When using P-Uo、Q-f
Sagging governing equation when, it is poor that there are equivalent reactances, so that inverter loop current is zero when stable state.
Step 2：Found out according to the relationship of equivalent impedance difference and circulation so that inverter loop current be zero equivalent resistance difference or
Person's equivalent reactance is poor；
Step 3：It is introduced into the equivalent impedance difference that inverter loop current is zero in system as virtual impedance, realizes
Inhibition to circulation.
The relationship of equivalent resistance difference and circulation in step 1 can be used following equation group to indicate
The relationship of equivalent reactance difference and circulation in the step 1 can be used following equation group to indicate
In above-mentioned two groups of equations, R1-R2It is poor for equivalent resistance, X1-X2It is poor for equivalent reactance, wherein α1Indicate inverter 1
Output electric current is ahead of the phase of load current, α2Indicate that inverter 2 exports the phase that electric current lags behind load current, θLIt is negative
Carry impedance angle.
The inverter equivalent resistance difference or equivalent reactance difference for making that circulation is zero in step 2 are to obtain in the following way
's：
In real system, equivalent impedance is generally difficult to measure, and also suffers from the influence of the factors such as temperature and change,
Therefore accurately cannot inhibit circulation by way of precalculating virtual impedance, by using phaselocked loop obtain export electric current with
The phase of load current, input of the difference of the two phase as adjuster, by the output electric current phase of adjuster control inverter
Position follows load current phase, and the output of adjuster is that required equivalent impedance is poor.
Contain harmonic components in usual inverter output current and load current, phaselocked loop locking phase can be had an impact, therefore
Fundamental component in output electric current and load current, the transmitting of used bandpass filter are extracted using a kind of bandpass filter
Function is
Wherein, ωfFor the centre frequency of bandpass filter.
Claims (4)
1. a kind of circulation inhibition method of three-phase inverter in sagging control process, it is characterised in that：Include the following steps：
Step 1：According to used sagging governing equation, equivalent impedance required for determining is poor：When using P-f, Q-UoUnder
When vertical governing equation, it is poor that there are equivalent resistances, so that inverter loop current is zero when stable state；When using P-Uo, Q-f sagging control
When equation, it is poor that there are equivalent reactances, so that inverter loop current is zero when stable state；
Step 2：Found out according to the relationship of equivalent impedance difference and circulation so that inverter loop current be zero equivalent resistance difference or wait
It is poor to imitate reactance；
Step 3：It is introduced into the equivalent impedance difference that inverter loop current is zero in system as virtual impedance, realizes to ring
The inhibition of stream.
2. a kind of circulation inhibition method of the three-phase inverter according to claim 1 in sagging control process, feature
It is：The relationship of equivalent resistance difference and circulation in the step 1 can be used following equation group to indicate：
The relationship of equivalent reactance difference and circulation in the step 1 can be used following equation group to indicate
In above-mentioned two groups of equations, R1-R2It is poor for equivalent resistance, X1-X2It is poor for equivalent reactance, wherein α1Indicate that inverter 1 exports
Electric current is ahead of the phase of load current, α2Indicate that inverter 2 exports the phase that electric current lags behind load current, θLFor load resistance
Anti- angle,For each inverter output current,For load current.
3. a kind of circulation inhibition method of the three-phase inverter according to claim 1 in sagging control process, feature
It is：The inverter equivalent resistance difference or equivalent reactance difference for making that circulation is zero in the step 2 are to obtain in the following way
's：
The phase of output electric current and load current is obtained by using phaselocked loop, the difference of the two phase is as the defeated of adjuster
Enter, load current phase is followed by the output current phase of adjuster control inverter, the output of adjuster is required etc.
Imitate impedance contrast.
4. a kind of circulation inhibition method of the three-phase inverter according to claim 2 in sagging control process, feature
It is：It is describedWithFor the electric current fundamental component after bandpass filter extracts, wherein used by bandpass filter
Transmission function be：
Wherein, ωfFor the centre frequency of bandpass filter.
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| CN201810622245.6A CN108879757B (en) | 2018-06-15 | 2018-06-15 | Circulating current restraining method for three-phase inverter in droop control process |
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| CN201810622245.6A CN108879757B (en) | 2018-06-15 | 2018-06-15 | Circulating current restraining method for three-phase inverter in droop control process |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103151785A (en) * | 2013-04-02 | 2013-06-12 | 湖南大学 | Multi-converter parallel circulating current restraining method with quick and reactive support |
| CN103227581A (en) * | 2013-05-10 | 2013-07-31 | 湖南大学 | Inverter parallel harmonic wave ring current restraining method for controlling harmonic wave droop |
| CN104092242A (en) * | 2014-07-15 | 2014-10-08 | 上海电力学院 | Inverter parallel control method based on controllable virtual impedance |
| US20170077707A1 (en) * | 2015-09-11 | 2017-03-16 | Enphase Energy, Inc. | Method and apparatus for impedance matching in virtual impedance droop controlled power conditioning units |
| CN107181281A (en) * | 2017-06-22 | 2017-09-19 | 同济大学 | Circulation inhibition method between a kind of isolated island microgrid shunt chopper |
-
2018
- 2018-06-15 CN CN201810622245.6A patent/CN108879757B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103151785A (en) * | 2013-04-02 | 2013-06-12 | 湖南大学 | Multi-converter parallel circulating current restraining method with quick and reactive support |
| CN103227581A (en) * | 2013-05-10 | 2013-07-31 | 湖南大学 | Inverter parallel harmonic wave ring current restraining method for controlling harmonic wave droop |
| CN104092242A (en) * | 2014-07-15 | 2014-10-08 | 上海电力学院 | Inverter parallel control method based on controllable virtual impedance |
| US20170077707A1 (en) * | 2015-09-11 | 2017-03-16 | Enphase Energy, Inc. | Method and apparatus for impedance matching in virtual impedance droop controlled power conditioning units |
| CN107181281A (en) * | 2017-06-22 | 2017-09-19 | 同济大学 | Circulation inhibition method between a kind of isolated island microgrid shunt chopper |
Non-Patent Citations (1)
| Title |
|---|
| 耿志清等: "逆变器并联运行及均流技术研究", 《陕西电力》 * |
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