Analysis and assessment of modular multilevel converter internal control schemes

Wang, Shuren and Adam, Grain P. and Massoud, Ahmed M. and Holliday, Derrick and Williams, Barry W. (2019) Analysis and assessment of modular multilevel converter internal control schemes. IEEE Journal of Emerging and Selected Topics in Power Electronics. ISSN 2168-6777 (https://doi.org/10.1109/JESTPE.2019.2899794)

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Abstract

Adoption of distributed submodule (SM) capacitors in a modular multilevel converter (MMC) necessitates complex controllers to ensure the stability of its internal dynamics. This paper presents comprehensive analysis and assessment of different proportional resonant (PR)-based control schemes proposed to stabilize the internal dynamics and ensure ac and dc sides power quality of the MMC within a dc transmission system. With the consideration of passive component tolerances, different energy and voltage based control schemes under various conditions are analyzed. It has been established that without vertical voltage balance control, unequal passive component values in the upper and lower arms of the same phase-leg may cause: unbalanced fundamental currents in the arms, unequal dc voltage across the arms, and fundamental oscillations in the common-mode currents that lead to fundamental frequency ripple in the dc link current. The theoretical analysis that explains this mechanism is presented, and is used to show that vertical voltage balancing is necessary for the nullification of arm voltage difference and suppression of odd oscillations caused by capacitive/inductive asymmetry between arms of the same phase-leg. Simulations support the theoretical analysis and the effectiveness of voltage balancing in ensuring correct operation, independent of tolerances of the MMC passive elements and operating conditions. A new direct method for elimination of fundamental oscillations in the common-mode and dc link current is proposed. Experimental results from a singlephase MMC prototype validate the presented theoretical discussions and simulations.

  • Item type:Article
    ID code:68721
    Dates:
    Date
    Event
    18 February 2019
    Published
    18 February 2019
    Published Online
    3 February 2019
    Accepted
    Notes:© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
    Subjects:Technology > Electrical engineering. Electronics Nuclear engineering
    Department:Faculty of Engineering > Electronic and Electrical Engineering
    Depositing user: Pure Administrator
    Date deposited:04 Jul 2019 09:39
    Last modified:15 Apr 2024 13:41
    URI:https://strathprints.strath.ac.uk/id/eprint/68721
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