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Flexible DC power grid grounding fault line selection method and device based on amplitude criterion

A ground fault, flexible DC technology, applied in electrical devices, fault locations, emergency protection circuit devices, etc., can solve problems such as small short-circuit current, branch power failure, DC voltage bias, etc., to achieve the effect of improving reliability

Pending Publication Date: 2022-08-05
STATE GRID SHANDONG ELECTRIC POWER +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] In the flexible DC power distribution system, if the AC side is grounded with high resistance, the DC side does not need other grounding measures. At this time, if a small ground fault occurs on the DC side, it will cause a DC voltage bias on the DC side, but the short-circuit current is small. The traditional method usually disconnects each branch one by one to find the grounding branch. Such a search method will cause a short-term power failure of the branch being tested.

Method used

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  • Flexible DC power grid grounding fault line selection method and device based on amplitude criterion
  • Flexible DC power grid grounding fault line selection method and device based on amplitude criterion
  • Flexible DC power grid grounding fault line selection method and device based on amplitude criterion

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Embodiment approach

[0048] Embodiments of the invention and features of the embodiments may be combined with each other without conflict.

[0049] When AC / DC adopts Space Vector Pulse Width Modulation (SVPWM), it usually produces a vertical third harmonic common mode voltage. If the neutral point of the AC side is grounded through high resistance, and the DC side is not grounded, the third harmonic will be generated during normal operation. It does not constitute a channel, and each branch has no third harmonic current. When a single-pole grounding fault occurs in any branch, the third harmonic voltage constitutes a channel, and the third harmonic voltage of the common mode is generated on the DC side, and the third harmonic common mode power is generated. .

Embodiment 1

[0051] This embodiment discloses a method for selecting a ground fault line of a flexible DC power grid based on an amplitude criterion. For a DC side ungrounded flexible DC power grid composed of a busbar, an AC / DC power supply branch and several load branches, the measured The DC common mode voltage of the bus is calculated as U com0 , its amplitude is the absolute value |U com0 |, the third harmonic common mode active power of each branch is obtained through measurement and calculation, and the third harmonic common mode active power of the i-th branch is set as P icom3 , whose amplitude is the absolute value |P icom3 |, when a ground fault occurs in the flexible DC power grid, the following criteria can be used to diagnose which line has a ground fault:

[0052] see attached figure 2 Criterion 1: If there is a DC common-mode voltage bias in the DC bus, that is: |U com0 |>k·U dc , and the common mode active power of the third harmonic of each DC branch is very small, ...

Embodiment 2

[0059] like figure 1 As shown, the purpose of this embodiment is to provide a ground fault line selection device for a flexible DC power grid based on an amplitude criterion, including:

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Abstract

The invention provides a flexible DC power grid grounding fault line selection method and device based on an amplitude criterion. The method comprises the steps of obtaining a flexible DC power grid bus DC common mode voltage absolute value and DC branch third harmonic common mode active power; and on the basis of the obtained data, a grounding fault branch is diagnosed by using an amplitude criterion, and after the grounding fault branch is diagnosed, the control system sends out a signal to cut off the DC branch. Therefore, short-time power failure of other branches due to the fact that the branches are disconnected one by one to find the fault branch is avoided, and the reliability of the direct-current power grid is improved.

Description

technical field [0001] The invention belongs to the technical field of DC power grid relay protection, and in particular relates to a method and device for selecting a ground fault line of a flexible DC power grid based on an amplitude criterion. Background technique [0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art. [0003] For the DC side ungrounded flexible DC grid composed of a busbar, an AC / DC power supply branch and several load branches, the technical problems that exist during fault diagnosis are: [0004] In the flexible DC power distribution system, if the AC side is grounded with high resistance, the DC side does not need other grounding measures. At this time, if a ground fault occurs on the DC side, a DC voltage bias will appear on the DC side, but the short-circuit current is very small. The traditional method usually uses disconnecting each branch one by ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/08G01R31/52G01R19/00G01R21/00H02H7/26
CPCG01R31/086G01R31/52G01R19/0084G01R21/002H02H7/268Y04S10/52
Inventor 秦文康徐习东牟磊孙振海李峰王黎王洋孙伟涛马晓路宋彦臻彭寅文宏成
Owner STATE GRID SHANDONG ELECTRIC POWER