Inductive modular multilevel converter of bridge arm reactors

Abstract

The invention relates to an inductive modular multilevel converter of bridge arm reactors and belongs to the field of power conversion. The modular multilevel converter comprises three phase units, and each phase unit comprises a sub-module set (SMs) and one bridge arm reactor (L); each sub-module set is formed by serially connecting multiple sub-modules, one end of each sub-module set is connected with the corresponding bridge arm reactor, the other end of each sub-module set is connected with a direct-current side positive pole or negative pole of an MMC, magnetic fluxes generated by common-mode components in upper and lower bridge arm currents in an iron core are superposed, differential-mode components in the upper and lower bridge arm currents are manually offset, accordingly upper bridge reactance and lower bridge reactance are superposed in the direct-current side, and the upper bridge reactance and the lower bridge reactance are mutually offset in the alternating-current side. Therefore, when the alternating-current side of the MMC is connected with a passive load, internal reactance of the MMC is reduced, and reactive power provided by the MCM is reduced.

Description

technical field [0001] The invention relates to a modular multilevel converter with bridge arm reactance and mutual inductance, belonging to the technical field of power conversion. Background technique [0002] Since the topology of the modular multilevel converter was proposed, it has received widespread attention. It adopts a modular design, which is less difficult in engineering technology, and the voltage level is easy to expand. Using multilevel technology, its AC side voltage The distortion is small, so that the AC filter can be omitted. Therefore, the modular multilevel converter has been widely used in flexible DC transmission. When the modular multilevel converter is connected to the power grid, its bridge arm reactor has three functions: 1. For the DC side, the reactors of the upper and lower bridge arms are connected in series to limit the The rising rate of the fault current; 2. For the AC side, the reactors of the upper and lower bridge arms are connected in p...

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Problems solved by technology

[0003] However, when the modular multilevel converter supplies power to the passive system, its equivalent reactance on the AC side is equivalent to the internal reactance of the power supply. During operation, it will consume a large amount of reactive power. Therefore, if it can be reduced If the equivalent reactance of the AC side is used, the capacity of the modular multilevel converter will be reduced when the same power load is supplied.

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