Shifting full-bridge modular multilevel converter

Abstract

The invention provides a shifting full-bridge modular multilevel converter MMC, which is formed by mutually connecting two full-bridge sub-modules FBSM in a shifting mode and comprises six IGBT switching tubes with antiparallel diodes, two capacitors and a diode. The shifting full-bridge modular multilevel converter MMC provided by the invention has the advantages of few used devices and simple control, can realize the balance of module capacitance and voltage under normal and fault conditions, can reduce half of measuring devices under normal conditions, and can quickly remove fault current under fault conditions, thereby being beneficial to system restart.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to a shift full-bridge modular multilevel converter MMC, which has the capability of clearing DC faults and self-equalizing voltage. Background technique [0002] Modular multilevel converter (MMC) has become a hot spot in the research and application of DC transmission due to its characteristics of no commutation failure, less harmonic content, and flexible control. However, the modular design makes each module independent of each other, resulting in unbalanced module voltages, which in turn causes unbalanced bridge arm voltages, resulting in circulation problems. In addition, short-circuit faults often occur in DC transmission systems based on overhead lines, but the DC line impedance is small and the fault current is large. How to make MMC-HVDC with DC fault ride-through capability is an urgent problem to be solved. [0003] At present, there are three main...

AI Technical Summary

Problems solved by technology

On this basis, some scholars have proposed two types of improved half-bridge sub-module topologies. After a short-circuit fault occurs on the DC side, the IGBT in the sub-module is blocked, and the unidirectional conductivity of the diode is used to block the fault current path, thereby preventing the sub-module capacitance. Discharge to the fault point, but this method cannot clear the fault current generated after the fault occurs and before the IGBT is locked

[0006] (2) After the module is locked, there is a reversely connected capacitor in the fault current path

[0010] Based on the above analysis, it can be seen that clearing the MMC DC fault current and improving the capacitor voltage balance of the MMC sub-module can be achieved by improving the sub-module topology, but most of the proposed improved sub-module topologies can only achieve one of the functions. Therefore, the study of a The new sub-module topology with both fault current clearing ability and capacitor voltage self-balancing ability is of great significance

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