Common-Mode Voltage Reduction of Modular Multilevel Converter Using Adaptive High-Frequency Injection Method for Medium-Voltage Motor Drives

• Published in: Energies (Basel) 2024-03, Vol.17 (6), p.1367
• Main Authors: Lee, Jae-Woon, Kim, Ji-Won, Lee, Chee-Woo, Park, Byoung-Gun
• Format: Article
• Language: English
• Subjects: adaptive high-frequency injection (AHFI); Analysis; arm current stress; common-mode voltage (CMV); Electric current converters; fluctuation coefficient; medium-voltage motor drive; Methods; modular multilevel converter (MMC)
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en17061367

This study proposes an adaptive high-frequency injection method (AHFI) aimed at mitigating common-mode voltage (CMV) on the AC side and alleviating current stress on power semiconductor devices within each arm of a medium-voltage motor propulsion system designed for modular multilevel converters. By adjusting the quantity of high-frequency components injected into each arm according to the fluctuation coefficient, the amplitude of injected high-frequency CMV and circulating currents can be reduced across medium to rated motor speeds. This approach enhances the start-up performance of medium-voltage motor drives while diminishing CMV effects on the motor side, resulting in decreased total harmonic distortion (THD) in the three-phase output waveforms. Furthermore, the effectiveness of the proposed AHFI method in SM voltage regulation and circulating current control under low-frequency operation is thoroughly analyzed. The validity of this method is established through comprehensive mathematical scrutiny and time–domain simulations performed using MATLAB/SIMULINK software (MATLAB version R2021b), along with real-time simulations conducted employing the real-time simulator OPAL/RT via hardware-in-the-loop simulation (HILS).