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Self-adaptive reclosing method for single-phase earth fault in bipolar direct-current power grid

A single-phase ground fault, direct current technology, applied to electrical components, circuit devices, emergency protection circuit devices, etc., can solve problems such as secondary overcurrent of DC lines, large AC short-circuit current, secondary damage to MMC, etc., to avoid secondary impact, strong resistance to transition resistance, and the effect of reducing design difficulty and cost

Inactive Publication Date: 2020-12-11
TIANJIN UNIV
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Problems solved by technology

In addition, when the surface of the wall casing is slightly polluted, moisture, rain, and lightning can easily cause flashover on the surface, which is also a common transient fault
If automatic reclosing is used to deal with the single-phase ground fault in the station, when reclosing is a permanent fault, it will cause secondary damage to the MMC: not only the large AC short-circuit current will appear again in the lower bridge arm of the MMC, but the DC line will also produce a secondary overshoot. electric current

Method used

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  • Self-adaptive reclosing method for single-phase earth fault in bipolar direct-current power grid
  • Self-adaptive reclosing method for single-phase earth fault in bipolar direct-current power grid
  • Self-adaptive reclosing method for single-phase earth fault in bipolar direct-current power grid

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Embodiment Construction

[0029] Technical scheme of the present invention is as follows:

[0030] ① Fault clearing strategy

[0031] The existing cleaning method based on switching off the AC circuit breaker has poor quickness, which makes the converter suffer from overcurrent and overvoltage hazards for a long time. The invention installs a DC circuit breaker on the metal circuit breaker, that is, a metal circuit breaker. After the fault MMC overcurrent is blocked, the fault current can be completely cleared within 4ms by switching off the DC circuit breaker (MRCB) and the metal return circuit breaker (MRCB), so that the time for the converter to suffer from overcurrent and overvoltage is greatly shortened , well protect the expensive power electronic devices in the converter.

[0032] ② Adaptive reclosing method

[0033] After adopting the fault clearing strategy described in ①, based on the characteristics of the neutral point potential on the valve side (△ side) of the transformer, the nature o...

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Abstract

The invention relates to a self-adaptive reclosing method for a single-phase earth fault in a bipolar direct-current power grid. The method comprises the following steps: (1) a fault clearing strategy: installing a direct-current circuit breaker (DCCB), i.e., a metal loop circuit breaker (MRCB), on a metal loop, and clearing a fault current through the switching-off of the DCCB and the MRCB afterthe overcurrent locking of a fault MMC; and (2) a self-adaptive reclosing method: based on the characteristics of the potential of a neutral point of a transformer valve side, namely a delta side, distinguishing the nature of the single-phase earth fault in the station so as to realize self-adaptive reclosing.

Description

technical field [0001] The invention relates to the field of relay protection and automation of power systems, in particular to a strategy for clearing single-phase grounding faults in a symmetrical bipolar topology MMC-HVDC power grid and an adaptive reclosing method. Background technique [0002] Due to the advantages of high output current waveform quality, low switching loss, high modularity and easy expansion, the flexible DC transmission technology based on modular multilevel converter (MMC) is widely used in the construction of multi-terminal DC grid and new energy connection. It has good application prospects in fields such as input and consumption, grid asynchronous interconnection and island power supply. The flexible DC system with symmetrical bipolar connection mode has more flexible operation mode and lower overvoltage level, which is in line with the development trend of high voltage, large capacity and multi-terminal DC grid, and has gradually become the mains...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H7/26H02H3/06
CPCH02H7/268H02H3/066
Inventor 薛士敏顾诚陈硕刘白冰
Owner TIANJIN UNIV
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