Method for realizing rapid conversion of ground loop and metal loop by using full-bridge MMC structure

Abstract

The invention provides a method for realizing rapid conversion of a ground loop and a metal loop by using a full-bridge MMC structure. By utilizing the characteristic of short conduction time of an IGBT, by means of the IGBT and a diode of the full-bridge MMC structure and through simple operation steps, the method realizes rapid conversion from the ground loop to the metal loop, so that the timeof direct current entering the ground is greatly reduced, and the influence on surrounding facilities is reduced; and meanwhile, under the condition of no grounding electrode or unavailability of thegrounding electrode, the reliability of the system can be improved, the probability of bipolar locking is reduced, and the stability of the system is improved.

Description

technical field [0001] The invention belongs to the field of high-voltage direct current transmission systems, and in particular relates to a method for fast switching metal loops of earth loops by using a full-bridge MMC structure. Background technique [0002] There are many modes of operation for the DC transmission system, including bipolar operation, single pole ground return line operation, and single pole metal return line operation. When one pole of DC is overhauled or fails, the other pole can continue to operate through the single-pole ground loop operation mode, which greatly improves the reliability of the DC transmission system. However, long-term earth return operation may easily lead to problems such as bias magnetization, excessive input and low current, so in the case of a fault, the single-pole earth return automatically transfers to the single-pole metal return operation mode, and at the same time, there is no grounding pole or the grounding pole cannot I...

AI Technical Summary

Problems solved by technology

However, long-term earth return operation may easily lead to problems such as bias magnetization, excessive input and low current, so in the case of a fault, the single-pole earth return automatically transfers to the single-pole metal return operation mode, and at the same time, there is no grounding pole or the grounding pole cannot In the case of unipolar blocking, it is necessary to quickly complete the conversion of the unipolar ground return line to the unipolar metal return line

[0003] The existing earth-to-metal scheme is often implemented by using a switch guide to close the metal circuit with an isolating switch and a metal circuit switch MRS to realize the diversion of the ground electrode loop current to the metal return line, thereby realizing the earth-to-metal conversion. This kind of switch takes a long time to close, generally in seconds, which cannot meet the needs of fast switching

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