Lightweight method and device for hybrid modular multilevel converter

Abstract

The invention provides a lightweight method and device for a hybrid modular multilevel converter. When the hybrid modular multilevel converter is stable, the third harmonic voltage correction amount is determined. The three-phase circulation suppression voltage correction is determined. The modulation wave voltage of the hybrid modular multilevel converter is determined, and the voltage fluctuation of a sub-module capacitor is reduced. The lightweight effect is obvious, and the hybrid modular multilevel converter can stably operate. According to the technical scheme provided by the invention, the third harmonic voltage correction is introduced, which solves the problem that voltage negative drop of a full bridge sub-module occurs when the modulation ratio increases; the hybrid MMC can pass a direct current fault without blocking; consideration are given to the characteristics of economy and control flexibility; the degree of the voltage fluctuation of the sub-module capacitor and the cost of the sub-module capacitor are greatly reduced on the premise of constant direct current bus voltage and transmission power; and the modular multilevel converter is lightweight.

Description

technical field [0001] The invention relates to the technical field of flexible direct current transmission, in particular to a light-weight method and device for a hybrid modular multilevel converter. Background technique [0002] Flexible DC transmission (VSC-HVDC) is a new generation of DC transmission technology following AC transmission and conventional DC transmission. Flexible DC transmission technology has the characteristics of independent adjustment of active power and reactive power, strong weak grid access and low voltage ride-through capability, low AC filtering and reactive power compensation requirements. Flexible DC transmission is an important equipment for building a smart grid. Compared with traditional methods, flexible DC transmission has stronger technologies in island power supply, capacity expansion and transformation of urban distribution networks, interconnection of AC systems, and grid connection of large-scale wind farms. The advantage is a strat...

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Problems solved by technology

[0004] In order to overcome the disadvantages of the hybrid modular multilevel converters in the prior art, which are caused by large fluctuations in the bus voltage, the lightening effect is poor, the present invention provides a hybrid modular multilevel converter lightweight Method and device, when the hybrid modular multilevel converter is stable, determine the third harmonic voltage correction amount, and then determine the three-phase circulating current suppression voltage correction amount according to the bridge arm current of the hybrid modular multilevel converter , and then determine the modulation wave voltage of the hybrid modular multilevel converter by the third harmonic voltage correction amount and the three-phase circulating current suppression voltage correction amount, and finally reduce the modulation wave voltage of the hybrid modular multilevel converter The capacitor voltage fluctuation of the sub-module is eliminated, the hybrid modular multilevel converter can run stably, and the effect of light weight is obvious

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