Five-level clamping cross type sub-module topological structure of modular multi-level converter

Abstract

The invention relates to a five-level clamping cross type sub-module topological structure of a modular multilevel converter, and belongs to the technical field of flexible direct-current power transmission. The MMC sub-module topology comprises an MMC sub-module topology, the MMC sub-module topology comprises sub-module output ends, the sub-module output ends are a voltage anode output end and a voltage cathode output end, the MMC sub-module topology further comprises a left half-bridge and a right half-bridge which are the same in structure, and the two half-bridges are connected through a power switch group S7 and a power switch group S8 which are crossed. The method has the rapid DC fault clearing capability, an AC switch does not need to be tripped off, the problems of capacitor voltage divergence possibly caused by long-time locking and action of an AC circuit breaker are avoided, and the non-locking mode is beneficial to rapid recovery of stable operation after the MMC breaks down.

Description

Technical field [0001] The present invention relates to a modular multilevel converter five-level clamp cross-type sub-module topology, in particular to a modular multilevel converter (Modular Multilevel Converter, MMC) with DC fault clearing capability. The five-level clamped cross-type sub-module topology belongs to the field of flexible DC transmission technology. Background technique [0002] The modular multi-level converter MMC type flexible DC grid based on overhead lines has the advantages of no commutation failure, small harmonic content and flexible controllability. It is expected to be used in new energy collection, distributed power supply access and cross-regional interconnection. play an important role. When a short-circuit fault occurs in the DC side line of the overhead line flexible DC grid, lower damping will cause the current to rise faster. Since the current does not cross zero, the fault clearing is more difficult than in the AC system. There are curre...

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Problems solved by technology

The traditional voltage equalization control method has a simple principle, and the capacitor voltage equalization control effect is relatively good. However, with the increase in the number of sub-modules, the calculation amount of the sorting algorithm increases, which leads to an overload of the controller. On the other hand, the capacitor voltage is small The fluctuation of the sub-module will also lead to repeated switching of the sub-module, making the switching frequency higher, further causing higher switching loss, and reducing the economy of MMC operation

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