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Low-current harm fault reclosing method for DCSM-MMC flexible DC system

A flexible DC, low current technology, applied in the direction of detecting faults, fault locations, electrical components, etc. by conductor type, can solve the problems of current secondary overcurrent hazards and low current hazards, achieve low current hazards and avoid secondary overcurrent hazards. The effect of current impact and avoiding capacitor discharge

Inactive Publication Date: 2016-07-27
TIANJIN UNIV
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Problems solved by technology

[0003] Aiming at the problem that the fault reclosing method in the current flexible DC system will cause the secondary current overcurrent hazard, the present invention proposes a low-current hazard fault reclosing method for the DCSM-MMC type flexible DC system, and realizes the DCSM-MMC type Flexible direct current transmission system, direct current fault reclosing method with low current hazard

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  • Low-current harm fault reclosing method for DCSM-MMC flexible DC system
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  • Low-current harm fault reclosing method for DCSM-MMC flexible DC system

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Embodiment Construction

[0017] Aiming at the topological structure characteristics of DCSM, the present invention proposes a new type of sub-module operation mode and the corresponding uncontrolled rectification operation mode of the converter, and accordingly designs a fault reclosing strategy with low current hazard, specifically content include:

[0018] Aiming at the characteristics of the DCSM topology, a corresponding new sub-module operation mode is proposed, which is called a half-bridge-like blocking mode in the present invention. Such as figure 1 (a) shows the implementation mode 1 of the half-bridge-like locking mode, which turns on IGBTT3 and locks T1-T2. At this time, the fault current can only flow through the freewheeling diode D2 and IGBTT3, and its physical characteristics are the same as those of the half-bridge sub-module in the locked state, so it is named as a half-bridge-like blocking mode. Such as figure 1 (b) shows the implementation mode 2 of the half-bridge-like locking m...

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Abstract

The invention discloses a low-current harm fault reclosing method for a DCSM-MMC flexible DC system. The method comprises the following steps: clearing a DC fault current through a locking converter and finishing deionization; feeding all DCSMs into a similar half-bridge locking mode; achieving an uncontrolled rectifying operation mode of a DCSM-MMC by the similar half-bridge locking mode of the DCSMs; if a DC line does not generate a current again, indicating that the fault disappears and immediately restarting the converter; and if the DC line generates the current again, indicating that the fault still exists, judging the fault as a permanent fault and immediately locking the converter. Compared with the prior art, the low-current harm fault reclosing method has the advantages that reclosing judgment can be achieved only by judging whether the current exists or not; when the permanent fault is reclosed, the converter can be quickly relocked under the condition of a very small line current, so that secondary over-current impact to the system caused by reclosing is effectively avoided; and the fault reclosing method has the positive effect of a low current harm.

Description

technical field [0001] The invention relates to the field of power system protection and control, in particular to a DCSM-MMC (diode-clampsub-module based modular multi-level converter, DCSM-MMC) type flexible direct current transmission system fault reclosing method with low current hazard. Background technique [0002] Flexible DC transmission using overhead lines is one of the effective ways to realize large-capacity DC transmission in the future. In the case of overhead line transmission, the DC fault rate is greatly increased, and the use of diode-clamp sub-module (DCSM) MMC (DCSM-MMC) instead of the traditional half-bridge MMC can realize the rapid removal of fault current. Due to the high probability of instantaneous faults on overhead lines, it is necessary to design a suitable fault reclosing strategy. At present, the existing reclosing strategy is mainly to unlock the converter station in zero power mode after a period of system de-ionization process, and judge wh...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H7/26H02H3/06H02J3/36G01R31/08
CPCY02E60/60H02H7/26G01R31/086H02H3/066H02J3/36
Inventor 李斌何佳伟
Owner TIANJIN UNIV
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