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Improved structure of MMC (Modular Multilevel Converter) current converter with direct-current fault current-limiting capacity and isolating method

A technology of DC fault and current limiting capability, applied in the output power conversion device, the conversion of AC power input to DC power output, electrical components, etc., can solve the problem of difficulty in isolation of DC faults, and reduce the operating speed and removal capacity. requirements, low cost, little effect of additional power loss

Inactive Publication Date: 2015-05-13
TIANJIN UNIV
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Problems solved by technology

[0005] Aiming at the difficult problem of DC fault isolation in the current flexible DC system, the present invention proposes an improved structure and isolation method based on the MMC converter with DC fault current limiting capability

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  • Improved structure of MMC (Modular Multilevel Converter) current converter with direct-current fault current-limiting capacity and isolating method
  • Improved structure of MMC (Modular Multilevel Converter) current converter with direct-current fault current-limiting capacity and isolating method

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Embodiment Construction

[0018] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, but the implementation scope of the present invention is not limited thereto.

[0019] The DC fault isolation method of the DC system based on the modular multilevel converter of the present invention, the specific content includes:

[0020] Some improvements are made to the structure of the MMC converter, that is, a current limiting module is added to each bridge arm of the MMC converter, such as figure 1 (a) shown. The current limiting module adopts a controllable switch T and a current limiting resistor R limiter way in parallel. figure 1 (a): T 1 , T 2 and D 1 、D 2 They are the IGBT transistor and the freewheeling diode inside a sub-module in the MMC; C is the DC capacitor in the submodule; T and D represent the IGBT transistor and the freewheeling diode in the current limiting module respectively, and R limiter is the current limiti...

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Abstract

The invention discloses an improved structure of an MMC (Modular Multilevel Converter) current converter with a direct-current fault current-limiting capacity and an isolating method; the isolating method comprises the steps: setting a current-limiting module in each bridge arm of the MMC current converter; judging whether the direct-current protection sends an actuating signal; if so, judging the fault occurrence of the present direct-current system and turning off a controlled switch T; putting a current-limiting resistor R limiter into a fault loop; triggering a direct-current circuit breaker to trip; if not, enabling the direct-current system to work normally and enabling the controlled switch T of the current-limiting module in each bridge arm to be always conducted. Compared with the prior art, the invention provides an effective, practical, simple and reliable isolating method for the fault of the DC system; and the requirements on the actuating speed and the cutting capacity of the direct-current circuit breaker are reduced by means of rapid and comprehensive fault current-limiting.

Description

technical field [0001] The invention relates to the field of power system protection and control, in particular to a DC fault isolation method for a DC system based on an MMC converter Background technique [0002] DC fault isolation is a key technology in the development of flexible DC systems. When a DC fault occurs in the flexible DC system, the fault current rises rapidly to a large overcurrent level, which will seriously affect the safe and reliable operation of the entire DC system, including the AC side, DC side and converter. In order to ensure the safe and reliable operation of the DC system, it is required to quickly isolate the faulty DC line within a few milliseconds of the fault, that is, a certain fault isolation method must be adopted to isolate the DC faulty line. [0003] At present, there are mainly three methods for isolating DC faults in DC systems: (1) When a DC fault occurs, the DC fault line is isolated by tripping the circuit breaker on the AC side. ...

Claims

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Application Information

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IPC IPC(8): H02M7/00H02H7/26
CPCH02H7/1255H02H7/268
Inventor 李斌何佳伟
Owner TIANJIN UNIV
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