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Distributed generator islanding detection method based on impedance measurement

A distributed power supply and island detection technology, applied in power supply testing, electrical components, emergency protection circuit devices, etc., can solve problems such as power imbalance, frequency, voltage changes, and complex operations, and achieve easy-to-implement results.

Inactive Publication Date: 2010-10-20
POWER GRID TECH RES CENT CHINA SOUTHERN POWER GRID +2
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  • Abstract
  • Description
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  • Application Information

AI Technical Summary

Problems solved by technology

[0004] ①Deterioration of power quality
The power imbalance in the small island system will cause changes in frequency and voltage, reducing power supply security and power quality
[0005] ②Threatening the safety of the public and operating personnel
Due to the uncertainty of the scope of the unplanned island, it is impossible to determine whether the system components and lines are live, which poses a threat to the safety of maintenance personnel, operating personnel and the public
[0006] ③ Changing the magnitude of the current flowing through the protection affects the correct action of the relay protection
[0007] ④The grounding point may be lost, threatening the insulation safety
Interlock tripping can reliably avoid all unplanned islands, simple and effective for systems with fixed topology, but it is costly and complex to operate

Method used

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  • Distributed generator islanding detection method based on impedance measurement
  • Distributed generator islanding detection method based on impedance measurement
  • Distributed generator islanding detection method based on impedance measurement

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Embodiment Construction

[0030] The technical solution of the present invention will be further described in detail below according to the drawings in the description and in combination with specific embodiments.

[0031] When the distributed power supply DG is connected to the system grid, the flow direction of the grid-connected line is not single due to the different matching degrees between the distributed power supply DG and the local load. This distribution network may absorb active power (reactive power) from the system, or may send active power (reactive power) to the system. So after being separated from the system, there is a power imbalance inside the island. by figure 1 Take Zone1 as an example. When the system fails, CB2 trips, and Zone1 is disconnected from the main system to form an isolated island. Power imbalance occurs in Zone1, causing a transient response process. If the adjustment margin and adjustment speed of DG1 are sufficient, a new steady state can be reached in a short pe...

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Abstract

The invention discloses a distributed generator islanding detection method based on impedance measurement, the principle utilizes the feature that a great change of system equivalent impedance occurs in DG synchronization and isolated network states, high-frequency voltage signals are injected at a synchronization contact point, and impedance change can be reflected by measuring voltage change, thus judging whether the system is connected with a large grid at present. In theory, the method is not influenced by load, has nothing to do with characteristics of a DG synchronization inverter, the DG number in the island in an islanding state and the topological state of a power grid, has easy realization of self-adaption setting and does not need coordination relationships. Experiment results show that the principle has excellent sensitivity, selectivity and rapidity.

Description

technical field [0001] The invention belongs to the power supply protection in the field of distributed power generation, and is applicable to various forms of distributed power sources. Background technique [0002] At present, when the grid connection line is disconnected due to failure or other reasons, the connection between the distributed power supply and the power distribution system will be lost, forming an electrical island. Generally speaking, after being separated from the main system, the power within the island is unbalanced. If the total capacity of the power supply in the island is much smaller than the total load, then the island cannot operate stably, and the island collapses after a short period of time. And if the total capacity of the power supply in the island is greater than or equal to the local load, a longer period of island operation may occur. [0003] Due to fault tripping and other reasons, the island operation with an uncertain range and occas...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H7/00G01R31/40
Inventor 胡玉峰吴小辰陈曦许健刘云秦应力承文新祝朝晖郭力王成山
Owner POWER GRID TECH RES CENT CHINA SOUTHERN POWER GRID
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