High-frequency break variable distance protection method of flexible DC power distribution system

Abstract

The invention discloses a high-frequency break variable distance protection method of a flexible DC power distribution system. The protection method comprises the following steps of 1, analyzing high-frequency fault characteristic when a bipolar short-circuit fault occurs in a photovoltaic access-containing flexible DC circuit with regard to the photovoltaic access-containing flexible DC circuit,and deriving transient high-frequency impedance of the system during a fault; 2, analyzing distribution characteristic of a voltage high-frequency fault component in the system during short circuit atdifferent positions, thereby obtaining a high-frequency break variable distance protection principle; and 3, analyzing influence of different circuit structures on high-frequency measurement impedance with regard to the problem of difficult in setting and matching of protection in the DC system, and performing protection configuration and setting calculation on the system.

Description

technical field [0001] The invention relates to the technical field of control and protection of a flexible DC power distribution system, in particular to a method for protecting the distance of a high-frequency sudden change in a flexible DC power distribution system. Background technique [0002] With the continuous development of distributed power generation, DC energy storage devices and the wide application of DC loads, DC power distribution systems have become a hot topic and development direction for research and application at home and abroad. Compared with AC power distribution, the DC power distribution system can reduce the intermediate links of distributed power generation systems and DC loads connected to the grid. It is flexible and efficient, has high power supply reliability, and good power quality, adapting to the development needs of future grid loads. In the flexible DC distribution network, the access of power electronic devices makes the system exhibit c...

AI Technical Summary

Problems solved by technology

One type of single-ended electrical quantity protection is conventional protection, including overcurrent, undervoltage, current / voltage differential, and distance protection. This type of protection does not require communication and has a fast action speed, but it cannot protect the entire length of the line. In the DC power distribution system, it is difficult to ensure selectivity, lack of fixed value calculation methods, and difficult to set; the other type is based on the special structure and device protection of the system, including the protection of the boundary of the construction of the current-limiting reactor, traveling wave protection, and distance measurement. Protection, etc. This type of protection needs to rely on special structures or devices, which may affect the economy and system response characteristics. It has special requirements for the primary system structure and is not universal

Double-ended electrical quantity protection includes electrical quantity longitudinal protection and directional longitudinal protection. This type of protection can realize full-line quick action, but requires real-time transmission of electrical quantity information, which requires high communication synchronization and is affected by line distributed capacitance.

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