MMC parallel topological structure applied to medium-voltage direct current system of ship

Abstract

The invention discloses an MMC parallel topological structure applied to a medium-voltage direct current system of a ship. MMC is formed by cascading of multiple half-bridge type MMC sub-module, wherein the alternating current terminal of the MMC is connected with the alternating current side of a ship electric power system electric generator, the direct current terminal of the MMC is connected with the direct current bus side of the ship electric power system; the multiple MMC are arranged, and thus the alternating current terminal and the direct current terminal of the multiple MMC are separately connected in parallel; and the half-bridge type MMC sub-module in the MMC is changed to be an inverse impedance type MMC sub-module. The MMC parallel topological structure has the advantages that shunting of the MMC is achieved when the power is increased, the limit value of power output is broken within a certain range, and the short circuit fault of the MMC direct current side is effectively processed via the introduction of the inverse impedance type MMC sub-module.

Description

technical field [0001] The invention relates to the technical field of medium-voltage DC power systems for ships, in particular to an MMC parallel topology structure for medium-voltage DC systems for ships. Background technique [0002] As a new type of converter, Modular Multilevel Converter (MMC) is composed of multiple MMC sub-modules cascaded, and the number of MMC sub-modules can be changed according to the voltage demand, with a high degree of modularity. The output harmonics are less, which has been widely concerned in the DC transmission system. [0003] Compared with traditional diode rectifiers, MMC is considered to be very suitable for marine medium-voltage DC power systems due to its obvious advantages (high output voltage quality, high efficiency, superior fault response, etc.). The research in the field of MMC abroad is relatively early, but the research on MMC in the medium voltage DC system of ships is still in its infancy. At present, the research on the a...

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Problems solved by technology

However, the rated current of the IGBT element in the MMC sub-module determines the rated current of the MMC bridge arm. The maximum rated current of the IGBT in the current MMC sub-module is 3600A (rated voltage is 1.7Kv). Under the current technical conditions, how to overcome the IGBT The obstacle of the current flow capacity of MMC is a difficult problem in the application of MMC in the medium-voltage DC power system of ships. In addition, in the MMC composed of traditional half-bridge MMC sub-modules, if a short-circuit fault occurs on the DC side, the IGBT anti-parallel The diode will form a path and cannot block the short-circuit current, which will cause great damage to the MMC and seriously affect the operation of the entire ship's medium voltage DC system (MVDC)

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