Modular cascaded multilevel converter control method and control device

Abstract

The invention discloses a modularized cascading type multi-level converter control method and device. The method comprises the steps that faulted submodules in a modularized cascading type multi-levelconverter are turned off, wherein according to the faulted submodules, DC / DC converter and / or cascading modules in the submodules break down; according to the number of cascading modules which normally work in phases, a certain number of zero-frequency components u0 are injected into three-phase modulation waves; according to the three-phase modulation waves obtained after the zero-frequency components are injected, active power transmitted by cascading modules which normally work in each phase is uniformly distributed. The purpose that active powers transmitted by single submodules in faultphases and non-fault phases are equal is achieved.

Description

technical field [0001] The invention relates to the technical field of power electronics, and more specifically, to a control method and a control device for a modularized cascaded multilevel converter. Background technique [0002] The modular cascaded multilevel converter refers to a multilevel converter formed by cascading multiple basic power units (also called sub-modules). figure 1 A typical modular cascaded multilevel converter topology is shown, each phase contains N sub-modules; the sub-modules include at least one DC / DC converter ( figure 1 There is only one DC / DC converter in the submodule as an example) and a cascade module, the DC side of the cascade module is connected to the at least one DC / DC converter; the AC side stage of each cascade module in each phase Connected to form a one-phase output, the three-phase output is connected to the grid in a star connection through a filter; the other side of each DC / DC converter is connected in parallel to form a commo...

AI Technical Summary

Problems solved by technology

When a sub-module fails, in order to ensure that the active power transmitted by the three phases A, B, and C is still equal, the existing method is to let the sub-module working normally in the faulty phase transmit greater active power, but this will cause The active power transmitted by a single submodule in the faulty phase is different from that in the non-faulty phase

For example, assuming that each phase has 6 sub-modules, when a sub-module fails, the active power transmitted by the remaining 5 sub-modules in the faulty phase will increase to 120% of the original, instead of the active power transmitted by each sub-module in the faulty phase unchanged, this power difference will lead to inconsistent heat dissipation requirements of the phase-to-phase DC / DC converter, which is not conducive to the overall performance optimization of the system

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