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MMC topology with DC short circuit fault current blocking ability

A fault current and DC short circuit technology, applied in the direction of converting AC power input to DC power output, electrical components, emergency protection circuit devices, etc. High, weak blocking ability, etc., to achieve the effect of short blocking time, low switching frequency, and avoiding overvoltage

Active Publication Date: 2019-04-12
SOUTHEAST UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] In order to solve the problem that the half-bridge MMC sub-module topology has no DC short-circuit fault clearing ability, the existing self-clearing sub-module topology has high cost, weak blocking ability, complex control, and large voltage stress of the DC side current-limiting reactor

Method used

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  • MMC topology with DC short circuit fault current blocking ability
  • MMC topology with DC short circuit fault current blocking ability
  • MMC topology with DC short circuit fault current blocking ability

Examples

Experimental program
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Effect test

specific Embodiment 1

[0042] Figure 2a and Figure 2b are respectively the current flow paths of a new sub-module SM in the first normal working mode when the current is forward and reverse.

[0043] Figure 2a Shown is the first normal working mode, when the current i sm When the positive terminal of the new sub-module SM flows in and the negative terminal flows out, the first switching tube T is controlled 1 , the second switching tube T 2 , the third switching tube T 3 and the second diode D 2 turn off, control the first diode D 1 conduction; and control the bridge arm reactance and the fourth switching tube T in the absorbing branch 4 , the fifth switching tube T 5 Both are off. At this time, the current i sm flows through the first diode D 1 , Capacitor C, to charge the capacitor C, so the output voltage of the new sub-module SM is the voltage between the two poles of the capacitor, that is, U sm =U C .

[0044] Figure 2b Shown is the first normal working mode, when the curren...

specific Embodiment 2

[0045] Figure 3a and Figure 3b are respectively the current flow paths of a new sub-module SM in the second normal working mode when the current is forward and reverse.

[0046] Figure 3aShown is the second normal working mode, when the current i sm When the positive terminal of the new sub-module SM flows in and the negative terminal flows out, the first switching tube T is controlled 1 , the third switching tube T 3 , the first diode D 1 and the second diode D 2 turn off, control the second switching tube T 2 conduction; and control the bridge arm reactance and the fourth switching tube T in the absorbing branch 4 , the fifth switching tube T 5 Both are off. At this time, the current i sm Flow through the second switch tube T 2 , the capacitor C is bypassed, so the output voltage of the new sub-module SM is zero, that is, U sm =0.

[0047] Figure 3b Shown is the second normal working mode, when the current i sm When the negative terminal of the new sub-mod...

specific Embodiment 3

[0050] combine Figure 5 , to describe in detail the working principle of current limiting of an MMC topology with DC short-circuit fault current blocking capability disclosed in the present invention.

[0051] When a DC-side bipolar short-circuit fault occurs in the converter station, the converter station will send out a blocking signal after detecting the fault signal to control the first switching tubes T of all new sub-modules SM in the upper and lower bridge arms of each phase. 1 and the second switching tube T 2 turn off, and control all bridge arm reactances and the fourth switching tube T in the absorbing branch 4 , the fifth switching tube T 5 conduction. At the same time, for the third switching tube T of the new sub-module SM in the upper and lower bridge arms of each phase 3 Adopt a back-voltage control strategy, that is, control all the third switching tubes T in the new module of the lower bridge arm of the phase with the highest voltage 3 All the third swi...

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Abstract

The invention discloses an MMC topology with DC short circuit fault current blocking ability, which relates to the technical field of modular multi-level converter. The topology consists of a new upper arm module, a reactance and absorption branch of the bridge arm, and a new lower arm module. The new modules of the upper and lower bridge arms in each phase are composed of n new submodules connected in series. Each new submodule outputs 0 or Uc voltages. The switches of the new submodules are all full-control devices IGBT, and the switches of the bridge arm reactance and absorption branch arebidirectional thyristors. In the event of a DC short circuit fault, the back-voltage control strategy is adopted to control the turn-on and turn-off of the third switch transistor in each new type sub-module, fast and effective blocking of AC system feed current is realized. At the same time, the bridge arm reactance and the absorption circuit absorbs the residual energy of the bridge arm reactorand the DC side current limiting reactor, and remarkably reduces the voltage stress of the DC side current limiting reactor and the bridge arm reactor, thus avoiding the overvoltage damage of the bridge arm reactor and the DC side current limiting reactor, and ensuring the safe operation of the device of the converter station.

Description

technical field [0001] The invention relates to the technical field of modular multilevel converters, in particular to an MMC topology with DC short-circuit fault current blocking capability. Background technique [0002] Modular multilevel converter MMC has been widely used in flexible DC projects due to its advantages of less harmonic content, low switching frequency and high reliability. However, when a bipolar short-circuit fault occurs on the DC side of the flexible DC grid, the DC short-circuit fault current rises rapidly, seriously endangering the safety of devices and the safe operation of the converter station. [0003] The traditional half-bridge MMC converter station has no DC fault clearance capability. Even if the sub-module is blocked, the feed-in of the AC system cannot be blocked, and the DC short-circuit current has no zero-crossing point, and the manufacturing process of the DC circuit breaker is immature and the cost is too high. Therefore, it is an effec...

Claims

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Application Information

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IPC IPC(8): H02M7/483H02M1/32H02H7/122
CPCH02H7/122H02M1/32H02M7/483
Inventor 梅军朱鹏飞管州何梦雪丁然吴夕纯范光耀葛锐王冰冰严凌霄陈武
Owner SOUTHEAST UNIV
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