Modular Multilevel Converter With Self-Energy Equalization for Medium Voltage AC Drive Applications

The modular multilevel converter (MMC) is a promising candidate for high-/medium-voltage high-power applications such as medium voltage ac drives due to its modularity, reliability, and scalability. The main challenge of a conventional MMC is low-frequency operation. Capacitor voltage ripple is inve...

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Bibliographic Details
Published in:IEEE transactions on industrial electronics (1982) 2021-12, Vol.68 (12), p.11881-11894
Main Authors: Elserougi, Ahmed A., Abdelsalam, Ibrahim, Massoud, Ahmed, Ahmed, Shehab
Format: Article
Language:English
Subjects:
Capacitance
Capacitors
Converters
Electric potential
Energy equalization
Energy levels
Energy utilization
Equalization
Legged locomotion
Medium voltage
medium voltage drive
modular multilevel converter
Modularity
Passive components
Ripples
Semiconductor devices
Topology
Voltage
voltage balance
Voltage control
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Summary:The modular multilevel converter (MMC) is a promising candidate for high-/medium-voltage high-power applications such as medium voltage ac drives due to its modularity, reliability, and scalability. The main challenge of a conventional MMC is low-frequency operation. Capacitor voltage ripple is inversely proportional to the operating frequency. Hence, operating at low frequency necessitates employing large submodule capacitances to limit voltage ripple or the utilization of energy equalization modules (EEMs). The first option negatively affects converter lifetime, and the second option requires a large number of semiconductor devices and isolating transformers. In this article, a modified MMC topology with self-energy equalization is proposed to ensure converter operation with balanced capacitor voltages with low ripple during zero-/low-frequency conditions. Operating with balanced capacitor voltages with low ripple is achieved by maintaining the same energy level in the involved upper and lower arms. A low device count alternative to the EEMs approach is proposed in this work. Detailed illustration of the operational concept and design of the associated passive components is presented. The performance of the proposed medium voltage ac drive is elucidated through simulation and experimental results.
ISSN:0278-0046
1557-9948
DOI:10.1109/TIE.2020.3045585