DC fault isolation method based on isolated modular DC transformer

Abstract

The invention relates to a DC fault isolation method based on an isolated modular DC transformer. The isolated modular DC transformer is based on an improved half bridge submodule: a set of anti-parallel structures formed by an IGBT VT1 and a diode VD1 is connected in series with a sub-module capacitor C, and is connected in parallel with an anti-parallel structure formed by a reverse resistance IGBT VT2 and a thyristor T2, the emitter of the VT1 is connected with the collector of the VT2, the collector and the emitter of the VT2 are respectively connected with the input end and the output endof the sub module, the reverse resistance IGBT VT2 adopts the IGBT with a reverse resistance function, namely a RB-IGBT, or adopts an IGBT to connect in series with the diode in the same direction; and moreover, when a direct current circuit generates faults, once the faults are detected, a turn-off command is sent to the sub-module, all the IGBTs are switched off, the conduction signals of the thyristor are cancelled, and the voltage modulation mode of the converter at the improvement side is changed so that the bridge arm in a converter at the fault side is subjected to zero crossing in order to achieve switch-off of the bridge arm so as to complete fault clearing and isolation.

Description

technical field [0001] The invention relates to the field of power electronics and power systems. Aiming at the difficulty in achieving the balance between fault isolation speed and system economy in the existing flexible DC system fault isolation method, the DC fault self-clearing capability is adopted under full consideration of equipment investment and loss. An isolated modular multilevel DC-DC transformer based on the improved half-bridge sub-module, and a DC fault isolation method is given. Background technique [0002] With the gradual depletion of traditional fossil energy, the world's environmental problems have become increasingly prominent, and countries have turned their attention to green and clean energy. Accelerating the transformation of energy types, adjusting the energy structure, and promoting the use of renewable energy have become the general trend. In the transmission and distribution of renewable energy, the DC transmission and distribution system has ...

AI Technical Summary

Problems solved by technology

[0010] Aiming at the problem that the fault development speed of the current DC distribution network is fast and the fault isolation is difficult, and the traditional DC transformer-based fault isolation method of the DC distribution network is difficult to ensure the fault isolation speed and have good economy. The present invention provides An isolated modular multilevel DC-DC transformer with DC fault self-clearing capability based on an improved half-bridge sub-module, and a corresponding fault isolation strategy is designed to realize fast DC fault clearing

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