CN102163837A - Method for protecting inverter in distributed generating system - Google Patents

Method for protecting inverter in distributed generating system Download PDF

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Publication number
CN102163837A
CN102163837A CN2011100567441A CN201110056744A CN102163837A CN 102163837 A CN102163837 A CN 102163837A CN 2011100567441 A CN2011100567441 A CN 2011100567441A CN 201110056744 A CN201110056744 A CN 201110056744A CN 102163837 A CN102163837 A CN 102163837A
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CN
China
Prior art keywords
protection
harmonic
inverter
overcurrent
current
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CN2011100567441A
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Chinese (zh)
Inventor
张艳霞
赵杰
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天津大学
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Priority to CN2011100567441A priority Critical patent/CN102163837A/en
Publication of CN102163837A publication Critical patent/CN102163837A/en

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Abstract

The invention belongs to the field of a distributed generating system of renewable energy sources, and relates to a method for protecting an inverter in a distributed generating system. The method is characterized by comprising overcurrent protection, overvoltage protection, undervoltage protection and overheating protection for a direct-current (DC) side, short-circuit protection and anti-isolated island protection for an alternating-current (AC) side, and fundamental overcurrent protection and secondary harmonic overcurrent protection for the DC side. The protection mode is as follows: DC current data at the DC side are collected, and a fundamental component and a secondary harmonic component are acquired after the data are processed by Fourier transform; overcurrent protection criterions of fundamental waves and secondary harmonic waves are set, and an overcurrent protector of the fundamental waves or the secondary harmonic waves acts when respective criterion is met. In the scheme provided by the invention, the principles are clear, and fault characteristics of the inverter are utilized sufficiently, thus being capable of quickly, flexibly and reliably reflecting short-circuit and disconnection faults of power tubes and a short-circuit fault of the AC side inside the inverter.

Description

Inverter guard method in the distributed generation system
Technical field
The present invention relates to the distributed generation system field of regenerative resource, particularly the inverter relay protective plan in solar energy, the wind energy distributed electricity generation system.
Background technology
Along with petering out of traditional fossil energy, green distributed generation systems such as new forms of energy such as solar energy, wind energy and tidal energy are applied more and more.Therefore, study the distributed grid-connected system that constitutes by new forms of energy and conventional electric power system and have important and practical meanings [1,2]
In the distributed generation system, voltage source inverter is most crucial, the most important equipment of whole system.Simultaneously, owing to the fragility of power switch pipe in the inverter and the complexity of control, make inverter become the easiest weak link that breaks down in the system, its integrity problem exists always [3,4]Therefore, inverter is carried out accident analysis, carry out the research of guard method, help improving the stability of grid-connected system and the useful life of equipment, have important significance for theories and economic worth.
The existing inverter protection mainly contains: the short-circuit protection of overcurrent protection, overvoltage protection, under-voltage protection, overtemperature protection and output AC side and the protection of anti-isolated island.The principle of these protections is simpler, does not make full use of the fault characteristic of inverter.At present, the bibliographical information that the protection of inverter is studied is also less.Document [5] adopts at DC side installing current sensor, realizes the protection of inverter short trouble by DC side electric current and threshold ratio, and its essence is exactly overcurrent protection.Document [6] utilizes current phasor track and electric current instantaneous frequency analytic approach that the open circuit fault of inverter pipe has been carried out signature analysis.Document [7-10] has proposed respectively short circuit of inverter single tube and the determination methods that opens circuit, but all is not applied in practice.
By last analysis as seen; imperfection is gone back in the protection of inverter at present; be necessary by analysis its fault characteristic; the protection scheme of invention new principle; be short-circuited or open circuit fault and AC side can quickly and reliably disconnect the connection switch of inverter when being short-circuited at inverter internal power pipe, with the safe operation of the conventional electric power system that guarantees to be incorporated into the power networks with distributed power source.
List of references
[1]Zhou?Dejia,Zhao?Zhengming,Eltawil,M.et?al.Design?and?control?of?a?three-phase?grid-connected?photovoltaic?system?withdeveloped?maximum?power?pomt?tracking[C]//?2008?23rd?Annual?IEEE?Applied?Power?Electronics?Conference?andExposition,APEC.Austin,TX,United?states,2008,973-979.
[2]Blaabjerg,F.Teodorescu,R.Liserre,M?et?al.Overview?of?Control?and?Grid?Synchronization?for?Distributed?Power?GenerationSystems.Industrial?Electronics,IEEE?Transactions?on,2006,53(5):1398-1409.
[3] Wu Xiaomei, Xu Xin, Nie Yixiong is based on the novel simulated model [J] of the three-phase voltage source type inverter of switch function. protecting electrical power system and control, 2009,37 (11): 74-77.
[4] Zhang Lanhong, Hu Yuwen, Huang Wenxin. the Malfunction Diagnoses ﹠ Tolerance Technology of inverter [J] in the three phase variable frequency drive system. electrotechnics journal, 2004,19 (12): 1-10
[5]Blaabjerg?F,Pedersen?J?K,Jaeger?U,et?al.Single?current?sensor?technique?in?the?DC?link?of?three-phase?PWM-VS?inverters:areview?and?a?novel?solution[J].IEEE?Transactions?on?Industry?Applications,1997,33(5):1241-1253
[6]Peuget?R,Courtine?S,Rognon?J?P.Fault?detection?and?isolation?on?a?PWM?inverter?by?knowledge-basedModel[J].IEEE?Transactions?on?Industry?Applications,1998,34(6):1318-1326.
[7]Mendes?A?M?S,Marques?Cardoso?A?J.Voltage?source?inverter?fault?diagnosis?in?variable?speed?AC?drives,by?tne?averagecurrent?Park′s?vector?approach[J].IEEE?International?Electric?Machines?and?Drives?Conference,1999:704-706
[8] Yang Zhonglin, Wu Zhengguo, Li Hui. based on the inverter open fault diagnostic method [J] of DC side current detecting. Proceedings of the CSEE, 2008,28 (27): 18-22.
[9] Cui Bowen appoints chapter. and the fault of converter based on Fourier transform and neural net detects and diagnosis [J]. electrotechnics journal, 2006,21 (7): 37-43.
[10] An Quntao, Sun Li, Zhao Ke waits the inverter open fault diagnostic method [J] based on switch function model. Proceedings of the CSEE, 2010,30 (6): 1-6.
Summary of the invention
The objective of the invention is to overcome the above-mentioned deficiency of prior art, a kind of inverter guard method that is applicable in the distributed generation system is provided.The scheme principle that the present invention proposes is clear, makes full use of the fault characteristic of inverter, can reflect the short trouble of power tube short circuit, open circuit fault and the AC side of inverter inside quick, sensitive, reliably.Technical scheme of the present invention is as follows:
Inverter guard method in a kind of distributed generation system, this guard method is except the short-circuit protection and the protection of anti-isolated island of the overcurrent protection, overvoltage protection, under-voltage protection and the overtemperature protection that comprise DC side and AC side, the first-harmonic overcurrent protection and the second harmonic overcurrent protection of DC side have also been increased, protected mode is as follows: gather the direct current data of DC side, obtain fundametal compoment and second harmonic component after it is handled through Fourier transform; The overcurrent protection criterion of setting first-harmonic and second harmonic is respectively: I 1〉=I Op.1And I 2〉=I Op.2, wherein, I iAnd I Op.i(i=1,2) are respectively the current amplitude and the protection setting value of first-harmonic or second harmonic.When satisfying separately criterion, first-harmonic overcurrent or the action of second harmonic overcurrent protective device.
Inverter guard method in the distributed generation system of the present invention, I Op.iWhen (i=1,2) all desirable inverter normally moves 5% of working direct current.
Beneficial effect of the present invention is as follows:
1, the present invention proposes to increase the scheme of first-harmonic overcurrent protection and second harmonic overcurrent protection on the basis of existing inverter protection, has made full use of the characteristics of inverter internal fault, and principle is clear, and it is reliable to be active in one's movements;
2, increase first-harmonic overcurrent protection and second harmonic overcurrent protection need not to add new hardware and can realize that prior art is accurate fast to the calculating of first-harmonic and second harmonic;
3, utilize first-harmonic overcurrent protection and second harmonic overcurrent protection can distinguish the fault type of inverter effectively, for the realization of the intelligent trouble diagnosis system of inverter is laid a good foundation.
Description of drawings
Fig. 1 photovoltaic parallel in system topological structure.
DC side current waveform when Fig. 2 inverter single tube opens circuit.
Embodiment
Below in conjunction with accompanying drawing the protection philosophy of institute of the present invention foundation is analyzed, technical scheme of the present invention is further specified.
For the inverter that accompanying drawing 1 provides, the present invention adopts the method for switch function, promptly utilizes formula (1) that its contingent various faults are analyzed
i dc=i aS a+i bS b+i cS c (1)
Wherein, i DcElectric current for DC side; i a, i b, i cFault current for the inverter AC side; S a, S b, S cBe switch function.Analysis result shows: when inverter internal power switch element was short-circuited, the DC side electric current enlarged markedly; When inverter internal power switch element opened circuit, DC side electric current present composition was listed in the table 1; When inverter AC side generation unsymmetrical short-circuit, the fault stable state fundamental current through type (1) of this side can transform to the DC side of inverter, and its electric current composition is as shown in table 1.
The DC side harmonic component of table 1 inverter different faults correspondence
As shown in Table 1, according to the inner fault type that takes place, the current component of heterogeneity can appear in the DC side of inverter.DC side current waveform when the inverter generation single tube that accompanying drawing 2 has provided grid-connected photovoltaic system opens circuit has tangible fundametal compoment.Because under normal operation, power tube is short-circuited and AC side the is short-circuited situation, the DC side of inverter does not all have fundametal compoment to occur.Therefore, the open circuit protection that utilizes fundametal compoment to constitute the inverter power pipe just has significant advantage.In like manner, when power tube one opened circuit mutually, DC side had bigger second harmonic (DC side also has second harmonic to occur during the AC side unsymmetrical short-circuit, but numerical value is less) to occur, utilizes second harmonic can effectively judge this kind fault.
Constitute protection fast in order to make full use of fault signature, it is as follows that the present invention proposes the inverter protection scheme of new principle.
DC side: except adopting existing overcurrent protection, overvoltage protection, under-voltage protection and overtemperature protection, increase first-harmonic overcurrent protection and second harmonic overcurrent protection, their operation equation is as follows
I 1≥I op.1 (1)
I 2≥I op.2 (2)
Wherein, I iAnd I Op.i(i=1,2) are respectively the current amplitude and the protection setting value of first-harmonic or second harmonic, I Op.iWhen (i=1,2) are all got inverter and are normally moved 5% of working direct current.
Overcurrent protection mainly reflects the short trouble of power tube; The open circuit fault of first-harmonic overcurrent protection formula (1) reflection power tube; The second harmonic overcurrent protection can reflect a phase open circuit fault of power tube.
AC side: adopt the protection of existing short-circuit protection and anti-isolated island.
The inverter protection scheme of the distributed generation system that the present invention proposes preferred forms as follows:
1, electric current and the voltage data of gathering this side by the current transformer and the voltage transformer of DC side gathered the electric current and the voltage data of AC side by the current transformer and the voltage transformer of AC side;
2, the current sampling data of DC side is handled in two steps.The one, the hall converter of process unipolarity power supply obtains direct current, and the 2nd, obtain fundametal compoment and second harmonic component through after the Fourier transform;
3, the voltage sample data of DC side obtain direct voltage through the hall converter of unipolarity power supply, and the current-voltage sampling data of AC side are respectively through obtaining fundametal compoment separately after the Fourier transform;
4, be opening circuit of inverter internal power pipe as if what take place, then first-harmonic overcurrent criterion formula (1) satisfies, first-harmonic overcurrent protection action; If what take place is that one of inverter internal power pipe opens circuit mutually, then second harmonic overcurrent criterion formula (2) satisfies, second harmonic overcurrent protection action; If what take place is the short circuit of inverter internal power pipe, then the overcurrent criterion of DC side (criterial equation and formula (1) are similar, adopt direct current) satisfies the overcurrent protection action.Overvoltage protection of DC side (criterial equation and formula (1) are similar, adopt direct voltage) and overtemperature protection (thermal relay) are by the corresponding operating mode of overvoltage criterion and overheated criterion reflection inverter; (criterial equation and formula (1) are similar for the short-circuit protection of AC side installing; adopt the AC side fundamental current) and anti-isolated island protection (criterial equation and formula (1) are similar, adopt AC side fundamental current and voltage) reflect fault and island state that the inverter AC side exports by corresponding overcurrent criterion and isolated island criterion.

Claims (2)

1. the inverter guard method in the distributed generation system, it is characterized in that, this guard method is except the short-circuit protection and the protection of anti-isolated island of the overcurrent protection, overvoltage protection, under-voltage protection and the overtemperature protection that comprise DC side and AC side, the first-harmonic overcurrent protection and the second harmonic overcurrent protection of DC side have also been increased, protected mode is as follows: gather the direct current data of DC side, obtain fundametal compoment and second harmonic component after it is handled through Fourier transform; The overcurrent protection criterion of setting first-harmonic and second harmonic is respectively: I 1〉=I Op.1And I 2〉=I Op.2, wherein, I iAnd I Op.i(i=1,2) are respectively the current amplitude and the protection setting value of first-harmonic or second harmonic, when satisfying separately criterion, and first-harmonic overcurrent or the action of second harmonic overcurrent protective device.
2. the inverter guard method in the distributed generation system according to claim 1 is characterized in that I Op.iWhen (i=1,2) are all got inverter and are normally moved 5% of working direct current.
CN2011100567441A 2011-03-09 2011-03-09 Method for protecting inverter in distributed generating system CN102163837A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102623968A (en) * 2012-03-14 2012-08-01 上海交通大学 Characteristic-harmonic-based protection method and system for high-voltage direct current transmission line
CN103364683A (en) * 2013-07-01 2013-10-23 东南大学 Method for detecting open-circuit fault of inverter circuit
CN104049159A (en) * 2014-05-16 2014-09-17 北京京东方能源科技有限公司 Fault detection method and device of inverter
CN104181474A (en) * 2014-07-22 2014-12-03 国家电网公司 Method for judging fault of photovoltaic grid connection inverter
CN104950207A (en) * 2014-03-25 2015-09-30 艾默生网络能源有限公司 Short circuit detecting method and device for photovoltaic inverter

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CN101399491A (en) * 2007-11-06 2009-04-01 中国科学院电工研究所 Overcurrent protection circuit for photovoltaic DC-to-AC converter
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US20090141522A1 (en) * 2007-10-10 2009-06-04 Solaredge, Ltd. System and method for protection during inverter shutdown in distributed power installations
CN101399491A (en) * 2007-11-06 2009-04-01 中国科学院电工研究所 Overcurrent protection circuit for photovoltaic DC-to-AC converter

Non-Patent Citations (2)

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MENDES, A.M.S.: "Voltage source inverter fault diagnosis in variable speed AC drives, by the average current Park.s vector approach", 《ELECTRIC MACHINES AND DRIVES》 *
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102623968A (en) * 2012-03-14 2012-08-01 上海交通大学 Characteristic-harmonic-based protection method and system for high-voltage direct current transmission line
CN102623968B (en) * 2012-03-14 2014-07-02 上海交通大学 Characteristic-harmonic-based protection method and system for high-voltage direct current transmission line
CN103364683A (en) * 2013-07-01 2013-10-23 东南大学 Method for detecting open-circuit fault of inverter circuit
CN103364683B (en) * 2013-07-01 2015-05-06 东南大学 Method for detecting open-circuit fault of inverter circuit
CN104950207A (en) * 2014-03-25 2015-09-30 艾默生网络能源有限公司 Short circuit detecting method and device for photovoltaic inverter
CN104950207B (en) * 2014-03-25 2017-08-29 艾默生网络能源有限公司 The method for detecting short circuit and device of a kind of photovoltaic DC-to-AC converter
CN104049159A (en) * 2014-05-16 2014-09-17 北京京东方能源科技有限公司 Fault detection method and device of inverter
CN104181474A (en) * 2014-07-22 2014-12-03 国家电网公司 Method for judging fault of photovoltaic grid connection inverter
CN104181474B (en) * 2014-07-22 2017-05-03 国家电网公司 Method for judging fault of photovoltaic grid connection inverter

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Application publication date: 20110824