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A hybrid ride-through method for DC short-circuit fault in mmc-mtdc system

A DC short-circuit and fault technology, applied in AC network circuit, emergency treatment AC circuit layout, emergency protection circuit device for limiting overcurrent/overvoltage, etc. It can solve problems such as stability, slow fault clearing speed, damaged IGBT, etc., to achieve the effect of safe and fast DC fault ride-through, improve the restart speed and reduce the impact.

Active Publication Date: 2022-07-19
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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  • Abstract
  • Description
  • Claims
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AI Technical Summary

Problems solved by technology

[0008] However, the current research on the non-blocking ride-through strategy is to control the DC output voltage of the converter to zero, so as to block the fault current. Although the non-blocking fault ride-through can be realized, the fault clearing speed is generally slow
Moreover, during the rapid and deep drop of the DC voltage, it is difficult to match the DC voltage established by inputting a negative level with the fault point voltage in real time. Once a large inrush current is generated, there is still a risk of blocking, and in severe cases, it may even damage the IGBT.
[0009] To sum up, the existing fault ride-through strategies for MMC-MTDC systems mainly target single-ended or double-ended systems, and neither the blocking fault ride-through strategy nor the non-blocking fault ride-through strategy can take into account the safety of the system and the restart of the converter station. the rapidity of

Method used

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  • A hybrid ride-through method for DC short-circuit fault in mmc-mtdc system
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  • A hybrid ride-through method for DC short-circuit fault in mmc-mtdc system

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Embodiment 1

[0052] The MMC-MTDC system includes multiple converter stations and multiple transmission lines, such as figure 1 Taking the four-terminal ring network shown as an example, the bipolar short-circuit fault of the DC transmission line is the most serious fault type of overcurrent. Therefore, this embodiment analyzes the fault characteristics of the four-terminal ring network after bipolar short-circuiting occurs.

[0053] Assuming that a bipolar short-circuit fault occurs at a certain point of the line connecting MMC1 and MMC4, the sub-module capacitors in each converter station will be discharged to the fault point through the DC line. Each converter station is equivalent to an RLC series circuit, and the calculation method of each equivalent element is:

[0054] (1)

[0055] in, R g , L g , C g ( g =1,2,3,4) are the converter stations respectively g The equivalent resistance, inductance and capacitance of , R 0g , L 0g , C 0g converter station g bridge arm r...

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Abstract

The invention discloses a hybrid ride-through method for DC short-circuit faults in an MMC-MTDC system, and relates to the technical field of power supply systems, including proposing a non-blocking fault ride-through strategy based on negative DC voltage control. On this basis, a hybrid crossing method is proposed, which does not block the converter station when no overcurrent occurs, actively blocks the converter station when the bridge arm overcurrent occurs, and removes the blocked converter station. , so that the unblocked converter station can continue to operate, realize the DC fault ride-through more safely and quickly, minimize the impact of the DC fault disturbance on the system, and help improve the anti-DC fault disturbance capability of the multi-terminal DC power grid.

Description

technical field [0001] The invention relates to the technical field of power supply systems, in particular to a hybrid ride-through method for direct current short-circuit faults in an MMC-MTDC system. Background technique [0002] Multi-terminal high voltage direct current (MTDC) system based on modular multilevel converter (MMC), referred to as MMC-MTDC system, is used in photovoltaic DC collection, distributed power access, and new energy base power over long distances. Transmission and other fields have broad application prospects. Modular multilevel converter (MMC) is composed of multiple sub-modules (SM) cascaded with the same structure, and has become the preferred converter topology for flexible DC transmission systems. MMC has many advantages, such as power supply to passive network and weak AC system, low harmonic content, easy expansion of modular design, etc., and has been successfully applied to many multi-terminal flexible DC projects. [0003] However, the v...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/36H02H9/02H02H9/04H02H7/26
CPCH02J3/36H02J3/001H02H9/02H02H9/04H02H7/268H02J2003/365Y02E60/60
Inventor 王毅魏子文王琛高玉华张振余欣洋
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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