CN106877392A - A kind of method for detecting island of photovoltaic grid-connected inverter - Google Patents
A kind of method for detecting island of photovoltaic grid-connected inverter Download PDFInfo
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- CN106877392A CN106877392A CN201510927347.5A CN201510927347A CN106877392A CN 106877392 A CN106877392 A CN 106877392A CN 201510927347 A CN201510927347 A CN 201510927347A CN 106877392 A CN106877392 A CN 106877392A
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- 238000001514 detection method Methods 0.000 claims abstract description 36
- 238000002347 injection Methods 0.000 claims abstract description 11
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- H02J3/385—
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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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
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
A kind of method for detecting island of photovoltaic grid-connected inverter, including isolated island detection, negative-sequence current injection and the detection of voltage harmonic aberration rate isolated island start three parts.The present invention proposes a kind of pouring-in island detection method of negative-sequence current based on voltage harmonic aberration rate and voltage unbalance factor, it is not injected into negative-sequence current under power network normal operation, and negative-sequence current is injected under power network abnormal conditions, compared with other active island detection methods have, strong interference immunity small to grid disturbance, fast isolated island detection speed the characteristics of.Matched with load power in PV power, remain to quickly and efficiently detect isolated island under rough sledding of the line voltage mains frequency all in the normal operation range of regulation.Distributed power source can be quickly out of service when the method is isolated island, or makes distributed power source that the change of islet operation control mode is transferred to by being incorporated into the power networks there is provided reference.
Description
Technical field
The present invention relates to a kind of photovoltaic combining inverter, more particularly to a kind of method for detecting island of photovoltaic grid-connected inverter.
Background technology
With the aggravation of earth environment pollution and petering out for conventional energy resource, the exploitation of new energy turn into current study hotspot.Photovoltaic generation (Photovoltaic, PV) still suffers from three big main bugbears as the important forms of electricity generation of one of which：Maximal power tracing control, interconnection technology and isolated island detection.Island effect refers to when power network is due to the reason interruption of power supply such as electric fault, maloperation or natural cause, distributed power generation (Distributed Generation, DG) system fails to detect power down mode and depart from power network, still electric energy is provided to load around, so as to form a uncontrollable self-energizing isolated island of Utilities Electric Co..Potential safety hazard may be brought during DG islet operations to user equipment, personal safety of the unplanned islet operation to maintainer simultaneously can also constitute potential threat, fast and effeciently detect island operation state and take rational control strategy, be conducive to improving the utilization ratio of power supply reliability and distributed power source.
At present, isolated island detection can be divided mainly into the island detection method based on communication and the island detection method based on local information.The status information that island detection method based on communication passes through wirelessly or non-wirelessly communications breaker, and then judge whether isolated island.Local island detection method can be roughly divided into the detection of passive type isolated island and active alone island detection.Wherein, distributed power source and power network points of common connection (Point of Common Coupling when passive type detection method mainly utilizes isolated island, PCC voltage), phase, frequency, harmonic content detect isolated island, passive type detection method is not required to increase additional hardware circuit, impact is not resulted in load, has the disadvantage there is larger check frequency (Non-Detection), when being matched with load power, voltage, frequency are maintained in normal operation range, based on OUV
Island detection method with OUF may fail.Active detection rule is periodically to judge whether isolated island occurs to points of common connection injection disturbing signal when DG is incorporated into the power networks.Due to the balanced action of power network phaselocked loop when power network normally runs, the disturbance will not be detected, and these injection disturbances of inverter will be accumulated during isolated island, circuit for detecting island will be triggered during beyond the scope of setting and detects isolated island generation.Active alone island detection method is also mainly based upon variation, frequency shift (FS) and phase offset principle, and its advantage is small check frequency, has the disadvantage that certain disturbance can be caused to power network when distributed power source is incorporated into the power networks.
The content of the invention
In order to overcome active island detection method to the problem in terms of grid disturbance, anti-interference, detection speed, the present invention proposes a kind of method for detecting island of photovoltaic grid-connected inverter.
The technical solution adopted for the present invention to solve the technical problems is：The present invention proposes and a kind of inject negative-sequence current by combining inverter and detect the quick island detection method of points of common connection voltage unbalance factor.The interference reduced to power network is injected by reasonable switching negative-sequence current, is not influenceed and without check frequency by unbalanced grid faults.
A kind of method for detecting island of photovoltaic grid-connected inverter includes that isolated island detection, negative-sequence current injection and the detection of voltage harmonic aberration rate isolated island start three parts.
Direct current is converted to by alternating current by inverter after isolated island detection grid-connected, unity power factor current control is taken when PV is grid-connected.
The negative-sequence current injection is by giving different forward-order current and negative-sequence current control injection PCC positive sequences, the sizes of negative-sequence current.
The voltage harmonic aberration rate isolated island detection starts total harmonic distortion factor (the Total Harmonic by detecting points of common connection voltage
Distortion, THD) judge whether isolated island occur.
The beneficial effects of the invention are as follows：The present invention proposes a kind of pouring-in island detection method of negative-sequence current based on voltage harmonic aberration rate and voltage unbalance factor, it is not injected into negative-sequence current under power network normal operation, and negative-sequence current is injected under power network abnormal conditions, compared with other active island detection methods have, strong interference immunity small to grid disturbance, fast isolated island detection speed the characteristics of.Matched with load power in PV power, remain to quickly and efficiently detect isolated island under rough sledding of the line voltage mains frequency all in the normal operation range of regulation.Distributed power source can be quickly out of service when the method is isolated island, or makes distributed power source that the change of islet operation control mode is transferred to by being incorporated into the power networks there is provided reference.
Brief description of the drawings
Fig. 1 isolated island detection principle diagrams.
Fig. 2 negative-sequence current injecting principles.
Fig. 3 isolated island testing processes.
Specific embodiment
Voltage harmonic aberration rate as " start-up criterion ", the injection for starting negative-sequence current are not injected into negative-sequence current when the THD of VCC is less than given definite value；Negative-sequence current is injected when voltage THD is more than given definite value, and by detecting that whether voltage unbalance factor is more than the definite value judgement island state for setting at PCC.
In Fig. 1, R, Lf are the resistance and inductance of inverter ac side filter, and Rs, Ls are main power network equivalent resistance and inductance, and it is in parallel that load model can be equivalent to RLC.The three-phase current of photovoltaic DC-to-AC converter output.DC voltage after the electric energy that photovoltaic battery array sends makes conversion through DC/DC conversion meets grid-connected requirement, and the maximal power tracing control strategy of conductance increment method is taken based in DC/DC conversion.Direct current is converted into alternating current finally by inverter grid-connected, unity power factor current control is taken when PV is grid-connected.
In Fig. 2, carry out three-phase reference current given during current control, the given electric current of output current tracking of inverter, by giving different forward-order currents and negative-sequence current, injection PCC positive sequences, the size of negative-sequence current can be controlled, C is the ratio of given forward-order current amplitude and given negative-sequence current amplitude.Combining inverter output is connected with power network in PCC, and the folding condition for switching K reflects the generation of isolated island, the three-phase voltage of points of common connection, including each harmonic component, fundamental positive sequence, negative phase-sequence and zero-sequence component.Its power output is calculated by the output voltage and output current that measure photovoltaic cell component in real time, the power and DC side power for ignoring AC when inverter power is lost are equal.Wherein, AC U are AC rated voltage, and give current waveform virtual value.
In Fig. 3, when there is unsymmetrical short-circuit, it is only very high in instant of failure and failure removal transient voltage percent harmonic distortion, can be dropped to by very short time harmonic aberration rate very low, that is the usual very little of its damping time constant, therefore in method, during using the definite value for reaching when voltage harmonic aberration rate setting, negative sequence component is added to inverter control circuit given value of current value, when the time that PCC voltage unbalance factors and total harmonic distortion factor exceed respective isolated island detection definite value is to sentence isolated island to occur more than the time delay definite value of setting, this time delay can not be mistaken for isolated island when should ensure grid disturbance, ensure that reliability of islanding detection is not judged by accident.
Claims (4)
1. a kind of method for detecting island of photovoltaic grid-connected inverter, it is characterised in that：Start three parts including isolated island detection, negative-sequence current injection and the detection of voltage harmonic aberration rate isolated island.
2. method for detecting island of photovoltaic grid-connected inverter as claimed in claim 1, it is characterised in that it is grid-connected that direct current is converted to alternating current by the isolated island detection by inverter, and unity power factor current control is taken when PV is grid-connected.
3. method for detecting island of photovoltaic grid-connected inverter as claimed in claim 1, it is characterised in that the negative-sequence current injection controls injection PCC positive sequences, the sizes of negative-sequence current by giving different forward-order current and negative-sequence current.
4. method for detecting island of photovoltaic grid-connected inverter as claimed in claim 1, it is characterised in that the voltage harmonic aberration rate isolated island detection starts and judges whether isolated island occur by detecting the total harmonic distortion factor of points of common connection voltage.
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| CN201510927347.5A CN106877392A (en) | 2015-12-14 | 2015-12-14 | A kind of method for detecting island of photovoltaic grid-connected inverter |
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| CN201510927347.5A CN106877392A (en) | 2015-12-14 | 2015-12-14 | A kind of method for detecting island of photovoltaic grid-connected inverter |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109100616A (en) * | 2018-10-23 | 2018-12-28 | 上海正泰电源系统有限公司 | A kind of detection method with the single-phase power-off of grounding transformer |
| CN111130134A (en) * | 2019-10-18 | 2020-05-08 | 国网冀北电力有限公司承德供电公司 | Island detection method based on system simulation |
| WO2021017547A1 (en) * | 2019-07-30 | 2021-02-04 | 华为技术有限公司 | Islanding detection method, device, and computer readable storage medium |
-
2015
- 2015-12-14 CN CN201510927347.5A patent/CN106877392A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109100616A (en) * | 2018-10-23 | 2018-12-28 | 上海正泰电源系统有限公司 | A kind of detection method with the single-phase power-off of grounding transformer |
| CN109100616B (en) * | 2018-10-23 | 2020-10-09 | 上海正泰电源系统有限公司 | Method for detecting single-phase power failure of transformer with grounding |
| WO2021017547A1 (en) * | 2019-07-30 | 2021-02-04 | 华为技术有限公司 | Islanding detection method, device, and computer readable storage medium |
| US11342757B2 (en) | 2019-07-30 | 2022-05-24 | Huawei Digital Power Technologies Co., Ltd | Islanding detection method and apparatus, and computer-readable storage medium |
| CN111130134A (en) * | 2019-10-18 | 2020-05-08 | 国网冀北电力有限公司承德供电公司 | Island detection method based on system simulation |
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Application publication date: 20170620 |