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Multi-objective optimization method based on genetic algorithm for MMC

A multi-objective optimization and genetic algorithm technology, applied in the field of multi-level power electronic converters, can solve the problems of capacitor voltage fluctuation, limitation, and bridge arm voltage affecting the modulation effect, etc., so as to reduce the peak value of capacitor voltage fluctuation and improve the fundamental frequency. The effect of the output amplitude

Active Publication Date: 2019-01-04
HUAZHONG UNIV OF SCI & TECH
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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

Method used

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  • Multi-objective optimization method based on genetic algorithm for MMC
  • Multi-objective optimization method based on genetic algorithm for MMC
  • Multi-objective optimization method based on genetic algorithm for MMC

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Embodiment 1

[0066] This example is used to illustrate that the bridge arm modulation voltage and capacitor voltage fluctuation can be effectively reduced by injecting common-mode voltage and circulating current, and the optimal injection amount of the two can be quickly found through the genetic algorithm to achieve multi-objective optimization. For a clearer description, the following analysis is carried out:

[0067] Taking the bridge arm above as an example, the switch function of the bridge arm is:

[0068]

[0069] The bridge arm current after injecting the circulating current is:

[0070]

[0071] Considering the unit power factor, the capacitor current can be obtained by the product of the bridge arm switching function and the bridge arm current:

[0072] i cp = S p · I rp

[0073] Combined with the above formula, the relationship between the sub-module capacitor voltage fluctuation and the common-mode voltage and circulating current injection is as follows:

[0074] ...

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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, Modular Multilevel Converter) has gradually become the most promising converter topology for HVDC transmission systems due to its advantages of highly modular structure, easy expansion, and low output voltage harmonics. In recent years, the voltage level and capacity of high-voltage direct current transmission projects have been increasing, 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. In the existing research, the method of injecting t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/483
Inventor 林磊李昂徐晨周雪妮
Owner HUAZHONG UNIV OF SCI & TECH
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