Investment evaluation model considering redundancy for flexible direct current converter

Abstract

The invention relates to an investment evaluation model considering redundancy for a flexible direct current converter, and belongs to the field of flexible direct current transmission. No special redundant sub-modules are set, all the sub-modules take turns to work, and the sub-modules which are not involved in the work are the redundant sub-modules for this round; in a working cycle, appropriaten sub-modules are selected from 2 (n+m) sub-modules of one phase to be put into work, and all the remaining redundant sub-modules are also involved in sub-module sorting and switching operation at all times; after a fault occurs, the redundant sub-module is put into work through a bypass fault sub-module to replace the faulty sub-module, and at most m sub-modules can be allowed to fail. It can beensured that an MMC is always in symmetrical operation. Compared with other schemes which have asymmetrical operation situations, the investment evaluation model has the advantages that the generatedharmonic circulating current is small. Compared with other schemes which have the problem that redundant sub-modules need to be charged before being put into use, the investment evaluation model hasthe advantages that the charging time is effectively shortened, and the input sub-modules are determined only through a selection strategy to complete the input action.

Description

technical field [0001] The invention relates to the field of flexible direct current transmission, in particular to an investment evaluation model of a flexible direct current converter considering redundancy. Background technique [0002] Since the emergence of the high voltage direct current (HVDC) technology based on the voltage source converter (Voltage source converter, VSC), the commutation components of the direct current transmission have been constantly innovating. Early HVDC adopts two-level or three-level converter technology, and a large number of IGBTs are directly connected in series to form valves. Although the circuit structure is simple, the technology is very difficult and the loss is high. Modular multilevel converter (MMC) is a new type of voltage source converter with a highly modular structure, easy to expand the system and realize redundant control, low switching frequency, and good output voltage waveform , has been widely used in flexible direct cur...

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Problems solved by technology

Low switching frequency, easy to expand the system and many other advantages, but the MMC is composed of multiple sub-modules cascaded, the output function largely depends on the sub-modules, once a sub-module fails, it will affect the normal operation of the MMC, thereby reducing the system The reliability of the operation, so a certain number of redundant sub-modules must be set. The redundant modules can replace the faulty sub-modules to ensure the safety and stability of the system. The research of MMC redundant operation control is particularly important.

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