Multi-terminal flexible DC power grid line direction pilot protection method

A DC power grid, multi-terminal flexible technology, used in emergency protection circuit devices, measuring electricity, electrical components and other directions, can solve problems such as long delay, misoperation, and failure to play, and achieve the effect of reliable identification

Active Publication Date: 2016-10-26
TIANJIN UNIV
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Problems solved by technology

[0007] Since the existing differential protection does not consider the capacitive current problem, any process that causes voltage changes, such as external faults and start-up processes, may cause malfunction. Therefore, in order to prevent malfunction, t

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  • Multi-terminal flexible DC power grid line direction pilot protection method
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Embodiment Construction

[0022] In order to make the object, technical solution and advantages of the present invention clearer, the implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0023] In the existing multi-terminal flexible DC system, the DC reactor is generally installed at the outlet of the converter station, so it cannot be used as a line boundary element to construct boundary differences. In the present invention, the DC reactor LP is installed at both ends of the DC line, and the specific installation method is as follows: figure 1 shown. This installation method is not only beneficial to the construction boundary protection, but also can effectively improve the fault current limiting capability, the rated fault ride-through capability of the system, and so on. Smoothing reactors are used to form the boundary elements of the DC transmission line. When faults occur inside and outside the DC transmission ...

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Abstract

The invention discloses a multi-terminal flexible DC power grid line direction pilot protection method. The method comprises steps: DC current and voltage at two ends of a DC reactor are measured and a DC current mutation rate di/dt and a voltage mutation rate du/dt are calculated; when the di/dt or the du/dt is larger than a threshold value K1-set and K2-set, a protection algorithm is started instantly; fault voltage at two sides of a DC reactor at a protection terminal is measured, and corresponding transient components UM_line and UM_bus (UN_line and UN_bus) are extracted; r1=UM_line/UM_bus (r2=UN_line/UN_bus) is calculated, and a fault direction is judged: if r1>1+epsilon (r2>1+epsilon), epsilon is a reliable margin, positive direction fault is judged and a direction signal RM is equal to 1 (RN=1), or otherwise, reverse direction fault is judged, and a direction signal RM is equal to 0 (RN=0); when RM&RN=1, internal fault is judged; and when RM&RN=0, external fault is judged. The method of the invention has the advantages that data synchronization is not needed; a sampling rate is lowly required; the fault resistance withstanding ability is strong; influences from line distributed capacitance do not exist; engineering implementation is facilitated; and the hardware investment cost is reduced.

Description

technical field [0001] The invention relates to the field of power system protection and control, in particular to a multi-terminal flexible direct current grid line direction longitudinal protection scheme based on the transient voltage amplitude ratio. Background technique [0002] As a very promising power transmission and distribution solution, flexible DC technology has the advantages of large power transmission capacity, long power transmission distance, flexible power regulation, narrow line corridors, and more convenient interconnection between power grids compared with AC power transmission. Therefore, it is very suitable for long-distance power transmission, distributed energy access, interconnection between asynchronous power grids, cable power supply in the center of large cities, and island power supply. [0003] DC line protection of flexible DC system is one of the key technologies in the development of flexible DC. The main difficulty of this technology lies...

Claims

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Application Information

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IPC IPC(8): H02H7/26G01R31/08
CPCG01R31/088H02H7/268
Inventor 李斌戴冬康何佳伟
Owner TIANJIN UNIV
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