Self coupled modular multilevel high-voltage DC-DC transformer and control method thereof

Abstract

The invention relates to a self coupled modular multilevel high-voltage DC-DC transformer and a control method thereof. An upper portion converter of the transformer adopts a full bridge sub module and half bridge sub module mixed modular multilevel one, a lower portion converter is a half bridge sub module type modular multilevel one, and energy interaction of the upper and lower portion converters is implemented in a self coupling manner. According to the determined alternate current transformer optimal rated transformation ratio and sub module selection principle, on the premise of maintaining the direct current failure isolating capability, the component requirements are lowered to the utmost extent, and the cost is reduced accordingly; on the basis of the precision feedback linear control strategy, the characteristics that the alternate current portion of a direct current transformer is free of power grid interference and system parameters can be measured accurately can be utilized completely, and the fine control performance is provided; by means of the fast direct current failure isolation, the direct current failure transmission and expansion of two direct current power grids can be prevented effectively; the transformer has the advantages that the transmission capacity is large, the direct current voltage level is high, and the transformer is adaptive to a high-voltage large capacity direct current power grid power conduction occasions.

Description

technical field [0001] The invention relates to the technical field of high-voltage direct current transmission, in particular to a self-coupling modular multi-level high-voltage direct-current-direct current transformer for high-voltage direct current transmission and a control method thereof. Background technique [0002] High-voltage direct current transmission (HVDC) technology has the advantages of fast and flexible power regulation, low cost of line channels, and low operating loss, and has broad application prospects. As more and more high-voltage DC transmission projects are put into operation, it is of great engineering significance to use DC transformers to realize the interconnection of DC systems of different voltage levels, thereby forming a multi-terminal DC or even DC grid with greater operational flexibility. [0003] DC-DC converters used in the field of low-voltage power distribution have various topological structures and mature technologies. However, in o...

AI Technical Summary

Problems solved by technology

2) DC fault isolation. For a DC fault on a certain side, the DC fault must be quickly and effectively processed and isolated to prevent the fault from being transmitted through the DC transformer, which will cause a chain reaction of the system and cause the system to collapse.

However, the existing technical means generally realize energy flow under the consideration of fixed DC voltage conversion, especially for DC fault isolation.

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