Optimization-Based Cell Selection Method for Grid-Connected Modular Multilevel Converters

Optimization-Based Cell Selection Method for Grid-Connected Modular Multilevel Converters

Modular multilevel converters (MMCs) are widely used in different applications. Due to low-loss operation, compactness, and high modularity, MMC is extremely attractive for high-voltage direct-current (HVDC) transmission systems. The HVDC station loss is highly related to the converter switching pul...

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Bibliographic Details
Published in:IEEE transactions on power electronics Vol. 31; no. 4; pp. 2780 - 2790
Main Authors: Hassanpoor, Arman, Roostaei, Amin, Norrga, Staffan, Lindgren, Markus
Format: Journal Article
Language:English
Published: New York IEEE 01-04-2016
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:
Capacitors
Heuristic
High-voltage direct-current (HVDC) transmission
HVDC transmission
Modular multilevel converter
modular multilevel converter (MMC)
Optimization algorithms
Power conversion
Simulation
Switches
Switching
Switching frequency
Switching loss
Tin
Voltage control
Zero current switching
switching frequency
zero-current switching
power conversion
switching loss
High-voltage direct-current (HVDC) transmission
modular multilevel converter (MMC)
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Summary:Modular multilevel converters (MMCs) are widely used in different applications. Due to low-loss operation, compactness, and high modularity, MMC is extremely attractive for high-voltage direct-current (HVDC) transmission systems. The HVDC station loss is highly related to the converter switching pulse pattern, which is generated by modulation algorithm and cell selection methods. This paper formulates the switching pulse pattern generation, as a versatile optimization problem. The problem constraints and objectives are formulated for HVDC applications and compared with similar problems in the field of computer science. To overcome the computational complexity in solving the introduced optimization problem, a heuristic method is proposed for cell selection algorithm. The method utilizes the current level in order to obtain lossless switching at zero-current crossings. The study of the proposed method, in a time-domain simulation platform, shows that the method can reduce the switching converter losses by 60% compared to carrier-based modulation, maintaining the same capacitor voltage ripple. Eventually, the practical functionality of the proposed method is verified in a real-time digital simulator, RTDS, for a 512-level converter in a point to point HVDC link. Although this paper focuses on HVDC, the mathematical model is applicable for any MMC application.
ISSN:0885-8993
1941-0107
1941-0107
DOI:10.1109/TPEL.2015.2448573