CN103995958B - Method for constructing harmonic wave impedance characteristic function - Google Patents
Method for constructing harmonic wave impedance characteristic function Download PDFInfo
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- CN103995958B CN103995958B CN201410166135.5A CN201410166135A CN103995958B CN 103995958 B CN103995958 B CN 103995958B CN 201410166135 A CN201410166135 A CN 201410166135A CN 103995958 B CN103995958 B CN 103995958B
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Abstract
The invention relates to a method for constructing a harmonic wave impedance characteristic function. The method comprises the steps that voltages at a common coupling point of distributed grid-connection power generation systems and currents connected into the distributed grid-connection power generation systems are collected; the fundamental wave impedance amplitude |Z1| at the common coupling point of the distributed grid-connection power generation systems and the harmonic wave impedance amplitude |Zk| at the common coupling point of the distributed grid-connection power generation systems are calculated, wherein k is a natural number larger than 1 and represents a corresponding harmonic order; according to a function (please see the specific formula in the specification), the harmonic wave impedance characteristic quantity phi (k) at the common coupling point is obtained. The method for constructing the harmonic wave impedance characteristic function is capable of obtaining the characteristic quantity for reflecting island load characteristics and lowering island error judgment occurring when grid frequency or voltages change or the multiple grid-connection power generation systems operate in parallel, and is wide in application range.
Description
Technical field
The present invention relates to extracting the data processing technique of characteristic quantity in distributed grid-connected electricity generation system in parameter, specifically relate to
And a kind of harmonic impedance characteristic function construction method.
Background technology
Distributed power generation refers in the live or close less generating set of electricity consumption situ configuration of user (generally below
30MW), to meet the needs of specific user, support the economical operation of existing power distribution network, or meet this two aspects simultaneously
Require.Continuous minimizing along with global fuel energy and its, dividing based on regenerative resource increasingly serious to environmental hazard
Cloth electricity generation system has obtained significant progress.However, also there are many Key technique problems urgently in distributed grid-connected electricity generation system
To be solved, particularly island phenomenon test problems.So-called island phenomenon refers in distributed grid-connected electricity generation system, when electrical network supplies
When electricity trips because of failure accident or power failure maintenance, the distributed grid-connected electricity generation system of each user side fails in time detection and goes out to stop
Electricity condition, thus itself is cut off electricity network, ultimately forms being made up of distributed grid-connected electricity generation system and its connected load
The isolated island electricity generation system of individual self-energizing.The generation of isolated island can threaten the safety of electrical network maintenance personal, impact distribution system
Protection switch misoperation, may cause to electrical equipment in reclosing to damage.
Existing island detection method is broadly divided into active alone island detection and passive type island detection method two class.No matter
Passive type and active alone island detection method, are required for the parameter at by detection point of common coupling and carry out corresponding data processing
Method obtains distinguishing the characteristic quantity of isolated island and non-isolated island, then thus to detect whether isolated island occurs.But, existing differentiation isolated island
With the characteristic quantity of non-isolated island if any the voltage effective value at point of common coupling, frequency, frequency change rate, voltage-phase etc., not
There is the characteristic embodying island load well, therefore when mains frequency, voltage changes or multiple distributed grid-connected generates electricity and is
During system parallel running, system is easy to isolated island erroneous judgement.
Content of the invention
The technical problem to be solved in the invention is how to provide a kind of harmonic impedance characteristic function construction method, application
The feature for distinguishing isolated island and non-island state of reflection island load characteristic in distributed grid-connected electricity generation system, can be obtained
Amount, reduce when mains frequency, voltage change or the isolated island that occurs during multiple distributed grid-connected electricity generation system parallel running by mistake
Sentence.
The above-mentioned technical problem of the present invention so solves, and builds a kind of harmonic impedance characteristic function construction method, its feature
It is, apply in distributed grid-connected electricity generation system, comprise the following steps：
Voltage at collection distributed grid-connected electricity generation system point of common coupling and the electricity of distributed grid-connected electricity generation system access
Stream；
Calculate the impedance of fundamental frequency amplitude at distributed grid-connected electricity generation system point of common coupling | Z1| and distributed grid-connected generating
Harmonic impedance amplitude at system point of common coupling | Zk|, wherein：K is the natural number more than 1, represents corresponding overtone order；
According to functionObtain the harmonic impedance characteristic quantity φ at point of common coupling
(k).
The harmonic impedance characteristic function construction method providing according to the present invention, described harmonic impedance characteristic quantity φ (k) is being divided
When the local load of cloth grid-connected system is pure resistor load, under isolated island stable state, there are φ (k)=0 or φ (k) close
0, its error range is 0-10%.
The harmonic impedance characteristic function construction method providing according to the present invention, described harmonic impedance characteristic quantity φ (k) is being divided
The local load of cloth grid-connected system is Q for quality factorfRLC in parallel (resistance-inductance-capacitance) load when, isolated island is steady
Determine to have φ (k)=Q under statefOr φ (k) is close to Qf, its error range is 0-10%.
The harmonic impedance characteristic function construction method providing according to the present invention, sentences according to harmonic impedance characteristic quantity φ (k) value
Determine distributed grid-connected electricity generation system and be in island state or non-island state.
According to the present invention provide harmonic impedance characteristic function construction method, distributed grid-connected electricity generation system be one with
On.
The harmonic impedance characteristic function construction method providing according to the present invention, described judgement is applied to the detection of passive type isolated island
In method or active alone island detection method.
The harmonic impedance characteristic function construction method providing according to the present invention, described distributed grid-connected electricity generation system is photovoltaic
Appointing in electricity generation system, wind generator system, fuel cell generation, single-phase of generating electricity system or three-phase distributed generation system
A kind of.
The harmonic impedance characteristic function construction method that the present invention provides, compared with prior art, has the advantage that：
1st, using distributed grid-connected TRT anti-islanding parallel connection RLC test load, there is specific quality factor qfSpy
Property carries out harmonic impedance characteristic function structure, thus having caught the substantive characteristics of island load well；
2nd, the characteristic quantity being drawn using the harmonic impedance characteristic function that the present invention builds, can embody island load well
Characteristic, distinguishes very big before and after isolated island occurs, thus laying a good foundation for the reliability and accuracy of isolated island detection technique；
3rd, the harmonic impedance characteristic function that the present invention builds is applicable not only to passive type isolated island detection method, is also applied for actively
Formula island detection method, and have wide range of applications, can be applicable to photovoltaic generating system, wind generator system, fuel cell etc. single
Phase or the distributed grid-connected system of three-phase.
Brief description
The present invention is described in detail further with specific embodiment below in conjunction with the accompanying drawings.
Fig. 1 is distributed grid-connected electricity generation system topological structure schematic diagram of the present invention；
Fig. 2 is artificial circuit characterizing magnitudes figure of the present invention.
Specific embodiment
In the preferred embodiment of the present invention, harmonic impedance characteristic function construction method is carried out according to the following procedure：
A), function builds
When isolated island situation occurs, the switch S in Fig. 1 disconnects, then point of common coupling (PCC) place's impedance during system stability
For：
Due to local loaded quality factorω0Represent local load resonant angular frequency, then distributed
Device output end impedance magnitude of generating electricity by way of merging two or more grid systems can be represented by formula (2).
Then at PCC, each harmonic impedance magnitude is represented by：
Wherein, ωPCCFor electric voltage frequency at PCC, corresponding variable in the case of isolated island is represented with subscript i, subscript 0 represents electricity
Net corresponding variable under normal circumstances.
Due to having under isolated island stable caseThen formula (3) can be write as：
Can be drawn with regard to Q according to formula (4)fExpression formula：
Known by formula (4)Then formula (5) can be expressed as：
According to formula (6), build harmonic impedance characteristic function φ (k), as shown in formula (7)：
B), the analysis of change and checking before and after characteristic function φ (k) isolated island
Understand have when distributed grid-connected electricity generation system is in isolated island stable state according to formula (7) and formula (6)And when island load only has resistance R,Obviously
φ can be obtainedi(k)=0 (k=2,3...).Under the normal connection of electrical network, the impedance at PCC point is much smaller than island load and hinders
Anti-, then harmonic impedance amplitude can change before and after electrical network disconnection and existAnd put down in power
In the case of weighing apparatus, impedance of fundamental frequency amplitude is equal before and after isolated island generation to beTherefore have under normal circumstances in electrical network
φ0(k)>φi(k) (k ∈ 2,3...), but the harmonic impedance characteristic at point of common coupling is in electrical network under normal circumstances and Runin Banished
Differ under condition, then can not possibly there is φ0(2)=φ0(3)=φ0(4)=.....Therefore by harmonic impedance feature letter
There is obvious difference in the characteristic quantity that number draws under island state and the normal connection of electrical network.
It is that method proposed by the present invention is verified, carried out simulating, verifying with 5000W single-phase full-bridge inverter, be used in combination
Inductance LgWith resistance RgSeries connection, as the equiva lent impedance of electrical network, takes L in artificial circuitg=0.1mH, Rg=0.001 Ω, isolated island
Load RLC value meets quality factor qf=2.5, consume active-power P=5000W.
Fig. 2 is that artificial circuit draws according to the characteristic function that harmonic impedance builds under isolated island stable state and non-isolated island stable state
Characterizing magnitudes figure, from figure it is apparent that under isolated island and non-isolated island stable state character pair value there is very big area
Not, in addition it is also seen that under isolated island stable state each characterizing magnitudes be no better than 2.5, such as do not consider to measure, calculation error can be recognized
It is that each characterizing magnitudes are equal to island load quality factor q under isolated island stable statef, thus demonstrating above theory analysis, also say
The characteristic quantity that the function that the bright present invention builds draws embodies island load characteristic well, and can preferably distinguish isolated island and non-
Island state.
The foregoing is only presently preferred embodiments of the present invention, all impartial changes done according to scope of the invention as claimed with
Modify, all should belong to the covering scope of the claims in the present invention.
Claims (10)
1. a kind of harmonic impedance characteristic function construction method is it is characterised in that apply in distributed grid-connected electricity generation system, including
Following steps：
Voltage at collection distributed grid-connected electricity generation system point of common coupling and the electric current of distributed grid-connected electricity generation system access；
Calculate the impedance of fundamental frequency amplitude at distributed grid-connected electricity generation system point of common coupling | Z1| and distributed grid-connected electricity generation system is public
Harmonic impedance amplitude at Coupling point altogether | Zk|, wherein：K is the natural number more than 1, represents corresponding overtone order；
According to function Obtain harmonic impedance characteristic quantity φ (k) at point of common coupling
Value.
2. according to claim 1 harmonic impedance characteristic function construction method it is characterised in that described harmonic impedance characteristic quantity
φ (k) distributed grid-connected electricity generation system local load be pure resistor load when, have under isolated island stable state φ (k)=0 or
φ (k) is close to 0.
3. according to claim 1 harmonic impedance characteristic function construction method it is characterised in that φ (k) close to 0 error model
Enclosing is 0-10%.
4. according to claim 1 harmonic impedance characteristic function construction method it is characterised in that described harmonic impedance characteristic quantity
φ (k) is Q in the local load of distributed grid-connected electricity generation system for quality factorfRLC in parallel load when, isolated island stable state
Under have φ (k)=QfOr φ (k) is close to Qf.
5. according to claim 1 harmonic impedance characteristic function construction method it is characterised in that φ (k) is close to QfError model
Enclosing is 0-10%.
6. according to any one of claim 1-5 harmonic impedance characteristic function construction method it is characterised in that according to harmonic wave hinder
Anti- characteristic quantity φ (k) value judges that distributed grid-connected electricity generation system is in island state or non-island state.
7. according to claim 6 harmonic impedance characteristic function construction method it is characterised in that described distributed grid-connected generate electricity
System is more than one.
8. according to claim 6 harmonic impedance characteristic function construction method it is characterised in that described judgement is applied to passively
In formula isolated island detection method or active alone island detection method.
9. according to claim 6 harmonic impedance characteristic function construction method it is characterised in that described distributed grid-connected generate electricity
System is any one in photovoltaic generating system, wind generator system or fuel cell generation.
10. according to claim 9 harmonic impedance characteristic function construction method it is characterised in that described distributed grid-connected is sent out
Electric system is any one in single-phase of generating electricity system or three-phase distributed generation system.
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Citations (4)
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|---|---|---|---|---|
| CN102749521A (en) * | 2012-07-18 | 2012-10-24 | 华北电力大学（保定） | Method for computing harmonic impedance of power system |
| CN102998535A (en) * | 2012-12-10 | 2013-03-27 | 华北电力大学（保定） | Method for computing harmonic impedance of system based on maximum likelihood estimation theory |
| CN103018534A (en) * | 2012-12-20 | 2013-04-03 | 广东电网公司电力科学研究院 | Method and system for determining harmonic voltage |
| CN103336205A (en) * | 2013-06-27 | 2013-10-02 | 新疆希望电子有限公司 | Island effect detection system and method during simultaneous injection of two harmonic current |
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| CA2885185A1 (en) * | 2012-10-12 | 2014-04-17 | Schweitzer Engineering Laboratories, Inc. | Coordinated high-impedance fault detection systems and methods |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102749521A (en) * | 2012-07-18 | 2012-10-24 | 华北电力大学（保定） | Method for computing harmonic impedance of power system |
| CN102998535A (en) * | 2012-12-10 | 2013-03-27 | 华北电力大学（保定） | Method for computing harmonic impedance of system based on maximum likelihood estimation theory |
| CN103018534A (en) * | 2012-12-20 | 2013-04-03 | 广东电网公司电力科学研究院 | Method and system for determining harmonic voltage |
| CN103336205A (en) * | 2013-06-27 | 2013-10-02 | 新疆希望电子有限公司 | Island effect detection system and method during simultaneous injection of two harmonic current |
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| 基于高频注入阻抗检测的孤岛检测研究;汤婷婷等;《电力电子技术》;20130331;第47卷(第3期);第70-72页 * |
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