Fault isolation and fault recovery method and system for medium-voltage DC distribution network

Abstract

The invention discloses a fault isolation and fault recovery method and system for a medium-voltage DC distribution network. A start end of a medium-voltage DC distribution line is provided with a DCcircuit breaker, and each segmented part of the line is provided with a load switch. The start end of the lien and each segmented part are provided with DC protection parts. A communication network isconfigured for the communication between the DC protection parts. When the medium-voltage DC distribution network has a fault, an overcurrent protection element of the DC protection part at the startend of the line operates, and a DC circuit breaker is switched off for eliminating the fault. After a fault current exceeds a fixed value, the DC protection part at each segmented part of the line transmits the fault current and the direction of the fault current to the adjacent DC protection part, and the DC protection part determines a fault point through the fault currents of the DC protectionpart and the adjacent DC protection part and the directions of the fault current, and then the DC protection part which is the nearest to the fault point operates, the load switch is switched off toisolate the fault. After the fault is isolated, the DC circuit breaker at the start end of line is switched on and the switch for power supply is switched on, so as to recover the power supply of a non-fault region.

Description

technical field [0001] The invention belongs to the field of direct current distribution networks of power systems, and in particular relates to a method and system for fault isolation and fault restoration of medium-voltage direct current distribution networks. Background technique [0002] At present, the medium-voltage DC distribution network is in the exploratory stage, and the medium-voltage DC distribution network has the following characteristics: [0003] 1. The DC power supply is relatively fragile [0004] When a fault occurs, the inverter will be blocked quickly, and the time is as short as a few hundred microseconds at the fastest. After the inverter is blocked, the entire line will lose power. The DC protection device needs to capture the fault characteristics within a few hundred microseconds and identify the point of failure. [0005] 2. It is difficult to guarantee selectivity [0006] The distribution network line is short, and the resistance of the DC di...

AI Technical Summary

Problems solved by technology

[0005] 2. It is difficult to guarantee selectivity

[0006] The distribution network line is short, and the resistance of the DC distribution line is small. When a fault occurs, the fault current at each place is similar. It can be blocked in a few hundred microseconds, and it is difficult to achieve the selectivity of faults through the coordination of time differences

[0007] 3. The DC power distribution line cannot run in a closed loop

[0008] Closed loop operation, when a fault occurs, both converters will be blocked, which will lead to the expansion of the fault range

[0009] Due to the characteristics of the medium-voltage DC distribution network, it is difficult to realize the fault isolation and fault recovery of the medium-voltage DC distribution network by using the over-current level difference and the time level difference. The present invention provides a set of new methods to solve this problem

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