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Lifetime and Reliability Improvements in Modular Multilevel Converters Using Controlled Circulating Current

Lookup NU author(s): Nasiru Kadandani, Dr Mohamed Dahidah, Dr Salaheddine Ethni, Dr Musbahu Muhammad



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Circulating current has been an inherent feature of modular multilevel converters (MMC), which results in second order harmonics on the arms currents. If not properly controlled, the circulating current can affect the lifetime and reliability of a converter by increasing the current loading, loss distribution, and junction temperature of its semiconductor devices. This paper proposes controlled circulating current injection as a means of improving the lifetime and reliability of an MMC. The proposed method involves modifying the reference modulating signals of the converter arms to include the controlled differential voltage as an offset. The junction temperature of the semiconductor devices obtained from an electro-thermal simulation is processed to deduce the lifetime and reliability of the converter. The obtained results are benchmarked against a case where the control method is not incorporated. The incorporation of the proposed control method results in a 68.25% increase in the expected lifetime of the converter and a 3.06% increase on its reliability index. Experimental results of a scaled down laboratory prototype validate the effectiveness of the proposed control approach.

Publication metadata

Author(s): Kadandani NB, Dahidah MSA, Ethni S, Muhammad M

Publication type: Article

Publication status: Published

Journal: Journal of Power Electronics

Year: 2021

Volume: 21

Pages: 1611-1620

Print publication date: 01/10/2021

Online publication date: 25/08/2021

Acceptance date: 03/08/2021

Date deposited: 09/08/2021

ISSN (print): 1598-2092

ISSN (electronic): 2093-4718

Publisher: Springer Nature


DOI: 10.1007/s43236-021-00297-7


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