Parameter design and control method of hybrid modular multilevel converter

Abstract

An embodiment of the invention discloses a parameter design and control method for a hybrid modular multilevel converter, which increases a modulation ratio of the hybrid modular multilevel converter to an optimal operation point through the coordination and cooperation of third harmonic voltage injection and a full-bridge sub-module negative level utilization method. The parameter design and control method comprises the steps of firstly, increasing the modulation ratio of the hybrid modular multilevel converter to the maximum extent through adopting a third harmonic voltage injection method, and secondly, increasing the modulation ratio to the optimal point through configuration of the cascade number of full-bridge sub-modules in bridge arms. When the hybrid modular multilevel converter outputs rated active power, the modulation ratio operates at an optimal operating point, so that a fundamental component of bridge arm power fluctuation can be changed into zero, the capacitance voltage fluctuation of the sub-module is greatly reduced, the capacitance use amount of the hybrid modular multilevel converter is greatly reduced, the number of required full-bridge sub-modules is reduced to the maximum extent, and the total cost and size of the device are reduced.

Description

technical field [0001] The invention relates to the technical field of voltage source converters and flexible direct current transmission, in particular to a parameter design and control method of a hybrid modular multilevel converter. Background technique [0002] Modular multilevel converter (English name is modular multilevel converter, referred to as MMC) has the advantages of easy realization of large number of levels, good harmonic performance, and modular design, and has become an inevitable choice for flexible DC transmission converters. . However, there is a large low-frequency power fluctuation on the MMC bridge arm, which will cause the voltage fluctuation of the sub-module capacitor. Therefore, it is necessary to design a large sub-module capacitance value to limit the voltage fluctuation within the allowable range. In existing projects, the volume ratio of the DC capacitor in the sub-module may reach more than 60%, and the cost ratio may reach more than 40%. T...

AI Technical Summary

Problems solved by technology

However, the third harmonic injection method has limited improvement on the maximum modulation ratio of MMC, and has limited influence on the optimization of MMC operating characteristics.

[0005] Although the third harmonic injection and negative level utilization can both change the relationship between AC and DC voltage conversion in hybrid modular multilevel converters, most of the existing studies deal with the two methods separately, and it is impossible to synthesize the two methods. Advantages Optimize the parameters and operating characteristics of hybrid modular multilevel converters, and optimize the overall cost and volume

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