Three-phase series ca-mmc and system with stabilizing capacitor bridge arm in flexible direct current transmission system

Abstract

The present invention provides a three-phase series-connected CA-MMC and a system provided with stabilizing capacitor bridge arms in a flexible direct current transmission system. It is composed of three-phase MMCs connected in series. Each phase MMC has four bridge arms, and the four bridge arms include the upper left bridge arm. , the lower left bridge arm, the upper right bridge arm and the lower right bridge arm, the upper left bridge arm is composed of HBSM, the lower left bridge arm is composed of HBSM, the upper right bridge arm is composed of a DC voltage stabilizing capacitor, and the lower right bridge arm is composed of HBSM and FBSM. The beneficial effects of the present invention are: the present invention utilizes a PR controller and a three-phase parallel MMC topological ladder wave thinning modulation mode, and further reduces the upper right bridge arm under the condition that the bridge arm current harmonics are fully suppressed. Capacitors, the combination of HBSM and FBSM is used in the lower right arm. When using the same or less number of sub-modules, the lower right bridge arm of each phase can generate more voltage levels, and the AC component in the capacitor of the upper bridge arm can be offset to ensure that each The phase DC side voltage is stable.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a three-phase series-connected CA-MMC and a system provided with voltage stabilizing capacitor bridge arms in a flexible direct current transmission system. Background technique [0002] With the development of remote areas and the large-scale application of flexible DC transmission technology, there is a demand for electricity from DC transmission lines in areas near the corridors of DC transmission systems, such as the construction of large-scale new energy power stations on some islands due to terrain and other reasons. It is not feasible. The shortage of energy severely limits the life and economic development of local residents; some islands are rich in clean energy but have no economical power transmission channels and ways to draw it out, resulting in waste of resources. Therefore, with the help of the existing DC transmission line corridor, the establishment and...

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Problems solved by technology

At present, the research on the three-phase series HBSM-MMC mainly focuses on its own operation mechanism, mathematical model, harmonic model and the DC voltage balance between the phases when the unbalanced fault occurs on the AC side, while the three-phase series CA-MMC There is no report on the application of topologies in DC transmission power substations

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