Fault ride-through method for DC unipolar grounding in multi-terminal flexible HVDC transmission system

A high-voltage direct current, power transmission system technology, applied in the direction of converting AC power input to DC power output, output power conversion device, emergency protection circuit device for limiting overcurrent/overvoltage, etc., can solve the problem of transient overvoltage Continue to maintain the fault power transmission and other problems to achieve the effect of eliminating fault transient overvoltage, improving active defense, and fast restarting after fault

Active Publication Date: 2019-05-14
HUAZHONG UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

It aims to solve the technical problem that the existing fault ride-through method applied to the multi-terminal flexible HVDC transmission system can only eliminate the transient overvoltage and cannot continue to maintain power transmission during the fault

Method used

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  • Fault ride-through method for DC unipolar grounding in multi-terminal flexible HVDC transmission system
  • Fault ride-through method for DC unipolar grounding in multi-terminal flexible HVDC transmission system
  • Fault ride-through method for DC unipolar grounding in multi-terminal flexible HVDC transmission system

Examples

Experimental program
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Effect test

example 1

[0132] The overhead line is used as the DC transmission line of the multi-terminal flexible HVDC transmission system. After detecting a single-pole ground fault, the MMC converter switches to the fault ride-through control mode: adjust the common mode command of the bridge arm reference signal of the faulty pole to be zero, the DC voltage command to be half of the rated value, and the active power command to be half of the rated value half. At the same time, by introducing the misphase angle γ between the differential mode component of the reference voltage of the upper bridge arm and the differential mode component of the reference voltage of the lower bridge arm, the balance of the capacitor voltage of the upper bridge arm sub-module and the balance of the capacitor voltage of the lower bridge arm sub-module are maintained, and The first additional reference voltage signal v is superimposed on the reference voltage of the faulty pole bridge arm zn1 , superimpose the second ...

example 2

[0145] The cable is used as the direct current transmission line of the multi-terminal flexible high voltage direct current transmission system. After detecting a single-pole ground fault, the MMC converter switches to the fault ride-through control mode: adjust the common mode command of the bridge arm reference signal of the faulty pole to be zero, the DC voltage command to be half of the rated value, and the active power command to be half of the rated value half. At the same time, the balance of the sub-module capacitor voltage between the upper and lower bridge arms is maintained by introducing the phase misalignment angle γ between the differential mode components of the reference voltage of the upper and lower arms, and the first additional reference voltage is superimposed on the reference voltage of the faulty pole arm signal v zn1 , superimpose the second additional reference signal v on the reference voltage of the sound pole arm zp1 . During the fault ride-throu...

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Abstract

The invention provides a fault ride-through method for direct current unipolar grounding of a multi-terminal flexible high-voltage direct current transmission system, which is realized through coordination and cooperation of an MMC based on low-impedance grounding and capable of negative level output and a mechanical direct current isolating switch. During the fault period, the fault transient overvoltage can be eliminated without sacrificing the controllability of the converter by adjusting the common-mode component of the reference voltage of each MMC converter bridge arm. At the same time, by superimposing the first additional reference voltage signal on the reference voltage of the faulty pole bridge arm, the current of the faulty pole bridge arm is controlled to be zero, so that the mechanical DC isolating switch can isolate the DC fault under the condition of zero current. It lays the foundation for the application of multi-terminal flexible direct current transmission system. During a fault, the MMC converter forms a loop through a sound DC bus bar-AC side low-impedance ground electrode-earth, which can maintain the transmission of half of the rated active power.

Description

technical field [0001] The invention belongs to the field of DC fault protection of a multi-terminal flexible high-voltage direct current transmission system, and more specifically relates to a fault ride-through method for DC unipolar grounding of a multi-terminal flexible high-voltage direct current transmission system. Background technique [0002] With the continuous improvement of the country's demand for energy sustainable development, my country's coal-based energy structure will gradually change to a structure in which hydropower, nuclear power, wind power, solar energy and other new energy coexist in the next few decades. The development of large-capacity long-distance advanced networking and transmission technology will help the cross-regional and complementary consumption of renewable energy, and at the same time provide strong support for promoting the construction of transmission channels from large energy bases to large power consumption areas. [0003] Under t...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/36H02H9/04
CPCH02H9/047H02J3/36H02M7/5388H02M7/4835
Inventor 林磊何震胡家兵
Owner HUAZHONG UNIV OF SCI & TECH
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