A kind of voltage balance control method and controller, mmc cascade system

Abstract

The invention discloses a voltage balance control method, a controller, and an MMC cascade system. The MMC bridge arm includes a plurality of sequentially connected sub-modules, including: a step of obtaining the capacitor voltage of the sub-modules, obtaining the capacitor voltage of each sub-module, and according to The switching state of the sub-module divides each sub-module into an input group and a cut-off group; the sorting step is to perform partial sorting in the input group and the cut-off group according to the capacitance voltage of the sub-modules in the group; the step of calculating the increase or decrease of the sub-module , to get the total number of sub-modules that need to be increased or decreased in this control cycle; the output step is to perform switching control on the sorted sub-modules in the input group and the cut-off group according to the total number of sub-modules that need to be increased or decreased; for some sub-modules Partial sorting is performed based on the size of the capacitor voltage, and the appropriate sub-modules are selected from the sorting results for switching. When the number of sub-modules in the MMC bridge arm is large, the number of sub-modules to be sorted is reduced, the sorting time is shortened, and the system control response speed is improved.

Description

technical field [0001] The invention relates to the field of power transmission engineering, in particular to a voltage equalization control method, a controller, and an MMC cascade system. Background technique [0002] With the continuous development of high-power power electronics technology, flexible DC transmission technology based on MMC (Modular Multilevel Converter) topology has been widely used. The system adopts modular design, which can be flexibly and conveniently expanded to different voltage levels. , and the harmonics are small, the waveform quality is high, and the footprint is small, so it has attracted more and more international and domestic power electronics engineering attention. [0003] In actual HVDC (high voltage direct current transmission) engineering applications, the number of sub-modules in the bridge arm of the system is large, and the higher the voltage level, the number of sub-modules will increase accordingly. In order to ensure the stable op...

AI Technical Summary

Problems solved by technology

The traditional sorting voltage equalization control method can ensure the smallest capacitor voltage deviation of sub-modules at any time, but with the increase of the number of modules, if all sub-modules need to be accurately sorted, the difficulty and time of sorting will increase, which will affect the system control response speed , it will also increase the switching frequency of the system, resulting in lower overall efficiency

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