A Multi-objective Optimization Method Based on Genetic Algorithm for MMC

Abstract

The invention discloses a multi-objective optimization method based on a genetic algorithm suitable for an MMC, which comprises the following steps: obtaining electrical parameters, obtaining capacitance value required by sub-module before optimization according to electrical parameters and set capacitance voltage maximum fluctuation rate epsilon; On the premise that the current level of the switching device is not improved before and after optimization, the constraint conditions of the bridge arm current before and after optimization are obtained. Based on the constraint conditions and electrical parameters, the Pareto solution set is obtained by genetic algorithm with the objective of minimizing the peak value of the bridge arm modulation voltage and the peak value of the capacitance voltage fluctuation of the sub-module. Taking the minimum peak value of bridge arm modulation voltage or the minimum peak value of capacitance voltage fluctuation of sub-module as the priority objective,the common-mode voltage injection amount and circulating current injection amount are determined from Pareto solution set, and the bridge arm modulation voltage after multi-objective optimization isobtained. Multi-objective optimization of MMC is realized. The present application utilizes genetic algorithms to obtain optimal common-mode voltage injection and circulating current injection volumes, thereby reasonably optimizing the MMC.

Description

Technical field [0001] The invention belongs to the technical field of multi-level power electronic converters, and more specifically, relates to a genetic algorithm-based multi-objective optimization method suitable for MMC. Background technique [0002] MMC (Modular Multilevel Converter) has gradually become the most promising converter topology for HVDC transmission systems due to its highly modular structure, easy expansion, and low output voltage harmonics. In recent years, the voltage level and capacity of HVDC transmission projects have continued to increase, which puts forward higher requirements for converters to improve output capacity and cost control. [0003] The MMC-HVDC project currently in operation mainly adopts the half-bridge sub-module HBSM (Half-Bridge SM) topology, and the output capacity is determined by the number of bridge arm sub-modules. Existing research uses the method of injecting common-mode voltage into the bridge arm voltage to achieve equivalent o...

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Problems solved by technology

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a genetic algorithm-based multi-objective optimization method suitable for MMC, thereby solving the existing problems in the prior art that injecting common-mode voltage will affect capacitor voltage fluctuations, injecting circulating currents will affect Changing the bridge arm voltage affects the effect of overmodulation, which limits the technical problems of the application of optimization methods in MMC

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