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DC bipolar short-circuit fault crossing method for modular multilevel converter

A modular multi-level, multi-level converter technology, applied in the direction of power transmission AC network, electrical components, output power conversion devices, etc.

Active Publication Date: 2015-09-09
TSINGHUA UNIV +1
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  • Abstract
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Problems solved by technology

[0006] The purpose of the present invention is to propose a DC bipolar short-circuit fault ride-through method for a modular multilevel converter to solve the problem of using a flexible DC transmission and distribution system (MMC-based HVDC) with a modular multilevel converter structure. The problem of DC bipolar short-circuit faults in the overhead line mode, during the period of DC short-circuit faults, the operation control of suppressing the short-circuit current of the DC side and providing dynamic reactive power support for the AC grid, that is, realizing its DC fault ride-through

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  • DC bipolar short-circuit fault crossing method for modular multilevel converter
  • DC bipolar short-circuit fault crossing method for modular multilevel converter
  • DC bipolar short-circuit fault crossing method for modular multilevel converter

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Embodiment Construction

[0077] The DC bipolar short-circuit fault ride-through method of the modularized multilevel converter proposed by the present invention comprises the following steps:

[0078] (1) Set the fault current action threshold I of the modular multilevel converter set , to measure the instantaneous value of the DC bus current I of the modular multilevel converter in real time dc , and the absolute value|I dc | with threshold I set Compare, if satisfy |I dc |>I set, it is determined that a bipolar short-circuit fault occurs on the DC bus, and the modular multilevel converter is switched to the fault ride-through operation mode;

[0079] (2) In the fault ride-through operation mode, measure the instantaneous value i of the three-phase current on the AC grid side of the modular multilevel converter at time t in real time x (t) (take the direction from the modular multilevel converter into the grid as the positive direction) and the instantaneous value of the three-phase voltage u x...

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Abstract

The invention relates to a DC bipolar short-circuit fault crossing method for a modular multilevel converter (MMC), and belongs to the electric power and electron technology and power transmission and distribution field. The method solves the problem of DC bipolar short-circuit faults when a MMC flexible DC power transmission and distribution system (MMC-based HVDC) employs overhead lines. For an MMC employing a unipolar sub-module, the MMC after detecting a DC bipolar short-circuit fault limits the DC short-circuit current within a relative low level, provides dynamic wattless support to an AC power grid, and effectively preserves and balances the energy of an inner capacitor of the converter to facilitate rapid starting of the converter after the fault is corrected. Compared with a conventional scheme of full-bridge sub-module-based MMC, the method is based on enhanced sub-module and mixed topology thereof. The cost is lower, and the economic performance is better.

Description

technical field [0001] The invention relates to a DC bipolar short-circuit fault ride-through method for a modular multilevel converter, and belongs to the fields of power electronics technology and power transmission and distribution. Background technique [0002] Compared with the traditional high-voltage direct current transmission technology, the flexible high-voltage direct current transmission technology uses fully-controlled semiconductor switching devices to realize the control of the converter, so it has the advantages of flexible control, free compensation of reactive power, and realization of conversion without relying on the AC system. It has been extensively researched and applied in recent years. Especially the flexible HVDC power transmission system based on the modular multilevel converter structure, with its highly modular structure, significantly reduced switching frequency and loss, eliminating the need for bulky multiple transformers, smaller AC and DC I...

Claims

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Application Information

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IPC IPC(8): H02M1/32H02J3/20H02J3/36
CPCY02E40/30Y02E60/60
Inventor 于心宇魏应冬姜齐荣
Owner TSINGHUA UNIV
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