Modular multi-level converter bridge arm bypass protection circuit against DC short circuit fault

Abstract

The invention discloses a bridge arm bypass protection circuit of a modularization multi-level converter aiming at a direct current short circuit fault, and belongs to a converter fault protection device range. The protection circuit is realized by arranging a bridge arm bypass, which is formed by serially connecting a bypass thyristor and a bypass resistor together, between the upper bridge arm and the lower bridge arm of every phase of the modularization multi-level converter. During common function, the bypass thyristor is in an off state, and the bridge arm bypass does not work. After the fault occurs, a sub-module IGBT is locked, and at the same time, the bypass thyristor is conducted, and because of the shunting function of the bridge arm bypass, fault current flowing through sub-module devices is reduced, and attenuation of direct current side current is also accelerated after trip-out of an alternating circuit breaker, and therefore fault recovery time is reduced, and a good fault protection function is provided for the devices and the alternating current system. For a system adopting the direct current circuit breaker, the protection circuit is used to reduce the fault current of the direct current side, and therefore a requirement on the switching-on / off of the current of the direct current circuit breaker is reduced, and economic performance and reliability are improved.

Description

technical field [0001] The invention belongs to the scope of protection devices for short-circuit faults of converters, in particular to a bridge arm bypass protection circuit for DC short-circuit faults of modularized multilevel converters. It is applicable to the case of DC bipolar short-circuit fault in the flexible HVDC transmission system with pseudo-bipolar structure, and the DC unipolar ground fault or bipolar short-circuit fault in the flexible HVDC transmission system with true bipolar structure. Background technique [0002] At present, modular multilevel converters generally use half-bridge sub-modules. When a DC short-circuit fault occurs in the system, the protection method is usually to block the sub-module IGBT first, and then use the AC circuit breaker to trip. In this protection mode, the only way to limit the fault current flowing through the sub-module device is to increase the inductance of the bridge arm. However, increasing the value of the inductance c...

AI Technical Summary

Problems solved by technology

In this protection mode, the only way to limit the fault current flowing through the sub-module device is to increase the inductance of the bridge arm. However, increasing the value of the inductance can reduce the fault current, but at the same time it prolongs the tripping of the AC circuit breaker. This will not only increase the time required for fault recovery, but may also have a serious impact on the stability of the AC system

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