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Direct-current island detection method based on specific frequency bus voltage positive feedback

A bus voltage and specific frequency technology, which is applied in the field of DC islanding detection based on the positive feedback of the specific frequency bus voltage, can solve the problem that the AC islanding detection method cannot be used directly, and achieves the effect of easy design, good compatibility and improved accuracy.

Active Publication Date: 2019-10-25
ZHEJIANG UNIV
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Problems solved by technology

Since only the bus voltage amplitude exists in the DC system to represent the operating state of the system, the AC islanding detection method cannot be directly used in the DC system, so an islanding detection method suitable for the DC system is needed to improve the islanding capability of the DC system

Method used

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  • Direct-current island detection method based on specific frequency bus voltage positive feedback
  • Direct-current island detection method based on specific frequency bus voltage positive feedback
  • Direct-current island detection method based on specific frequency bus voltage positive feedback

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Embodiment Construction

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention.

[0041] The equivalent model of the DC grid is as figure 1As shown, it is mainly composed of power management unit, voltage management unit and load. Distributed power sources in the DC grid, such as photovoltaic power generation and wind power generation, work in the maximum power point tracking mode in order to maximize the acquisition of clean energy, which can be equivalent to a power management unit. Since the capacity of the main grid is much larger than that of the distributed generation system, the grid-connected interface converter often acts as a voltage management unit to maintain the stability of the bus voltage of the system, thereby realizing the balance of power generation and power consumption in the DC system. When the grid-connected switch is closed, the system opera...

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Abstract

The invention discloses a direct-current island detection method based on specific frequency bus voltage positive feedback. The method mainly comprises three parts including a specific frequency bus voltage component extraction link, a specific frequency disturbance quantity injection link, a direct-current island judgment link; the specific frequency bus voltage component extraction link and thespecific frequency disturbance quantity injection link form a positive feedback mechanism in a power management unit control loop; in a direct-current grid connection mode, due to the control effect of a voltage management unit on a bus, the positive feedback mechanism loses efficacy, and the bus voltage is kept stable; in a direct-current grid island mode, a power management unit enables the busvoltage to generate self-oscillation of a specific frequency under the action of the positive feedback mechanism; and the direct-current island judgment link is used for judging whether a system is inan island mode or not according to the change tendency and the magnitude of a specific frequency bus voltage component. The method can rapidly detect the occurrence of a direct-current island, and can eliminate a detection blind area of a passive island method.

Description

technical field [0001] The invention belongs to the fields of distributed power generation, DC power grids, and AC-DC hybrid power grids, and in particular relates to a DC island detection method based on positive feedback of specific frequency bus voltage. Background technique [0002] With the continuous consumption of fossil energy, the problem of energy crisis has become increasingly prominent. Renewable energy generation will be the only way to replace fossil energy. With the rapid development of new energy power generation and electric vehicles, the proportion of DC source and load in the power grid is increasing. Compared with the AC grid, the DC grid has many advantages of high efficiency, low cost, and good power quality, and has become an important part of the modern power system. DC island detection is a key technology to ensure safe power supply after local islands are formed. [0003] The isolated island originates from the AC power grid, which refers to the ...

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Application Information

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IPC IPC(8): G01R31/08G01R31/00
CPCG01R31/086G01R31/00G01R19/2513H02J1/106H02J1/102H02J1/12H02J3/388G05B13/022
Inventor 李武华黄庆辉李楚杉杨贺雅顾小卫陈敏杨欢何湘宁
Owner ZHEJIANG UNIV
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