A snubber circuit for a half-full-bridge sub-module of a modular multilevel converter

Abstract

The invention discloses a buffer circuit of a half-full-bridge sub-module of a modular multilevel converter. The half-full-bridge sub-module includes a left half-bridge module, a right half-bridge module and a connecting circuit; it also includes three sets of RCD buffer circuits, Each set of RCD snubber circuits includes: a resistor and a diode connected in parallel and connected in series with a capacitor, and the cathode of the diode is connected to the anode of the capacitor. The present invention proposes a buffer structure of three sets of RCD snubber circuits. The first set of RCD snubber circuits suppresses the IGBT turn-off voltage spikes of the left half-bridge module, and the second set of RCD snubber circuits suppresses the IGBT turn-off voltage spikes of the right half-bridge module. The IGBT turn-off voltage peak of the connected circuit is suppressed by the third group of RCD snubber circuits, which simplifies the snubber circuit of the half-full bridge sub-module, and can better suppress the IGBT turn-off voltage while reducing the cost of the snubber circuit; the invention proposes RCD The parameter design of the snubber circuit can reduce the system cost and ensure that the IGBT turn-off overvoltage does not overshoot.

Description

technical field [0001] The invention belongs to the research field of IGBT snubber circuits, and more specifically relates to a snubber circuit of a half-full-bridge sub-module of a modularized multilevel converter. Background technique [0002] Modular Multilevel Converter (MMC) has the advantages of modular structure, easy packaging and expansion, small switching device stress and low output voltage harmonics, and has been applied in practical projects, such as the Transbay project in the United States, China's Zhoushan five-terminal flexible DC transmission project. [0003] According to different sub-module topological structures, modular multilevel converters are generally divided into three types: half-bridge type, full-bridge type and clamped double type. The Semi-Full Bridge Sub-module (SFB-SM) is a clamping dual-type sub-module, which consists of 7 IGBT anti-parallel diodes, with +2Uc, +Uc, 0 and -Uc four A level output capability. Compared with the full-bridge s...

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Problems solved by technology

[0008] In view of the defects of the prior art, the purpose of the present invention is to solve the technical problem of complex design and high cost caused by the need for a large number of IGBTs in the prior art half-full bridge sub-module

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