Novel Optimal Design of Arm Inductor for Modular Multilevel Converter Fed High Power Medium Voltage Drive

Abstract—

The modular multilevel converter (MMC) is considered to be emerging multilevel topology for medium to high power applications due to its modularity and highly reliable structure. However, large submodule (SM) capacitor voltage ripple and higher circulating current during variable frequency operation is the major drawback of the MMC. In the literature, higher-order harmonic elimination technique is presented to reduce SM capacitor voltage ripple and circulating current. In this article, effect of lower-order harmonics on circulating current is investigated. The effect of second-order fundamental frequency current harmonic I_2f on arm inductor is analyzed. Based on detailed analysis, an optimal design method for selection of arm inductor is proposed. Proposed optimal design is capable of reducing the circulating current under variable frequency range as well as SM capacitor voltage ripple remains under specified limit during entire variable frequency operation. A detailed MATLAB model of MMC fed high power medium voltage drive is developed. Experimental setup is also developed to check the effectiveness of proposed optimal design method. Reduction in circulating current and control of SM capacitor voltage ripple is observed for entire range of frequency.

Keywords:

• modular multilevel converter
• circulating current
• total harmonic distortion
• submodule capacitor voltage ripple
• variable frequency drive

Additional information

Notes on contributors

Divyesh J. Vaghela

Divyesh J. Vaghela received the B.E. degree in electrical engineering from Sardar Patel University in 2009 and M.E. degree in electrical engineering from The M.S. University of Baroda, Vadodara in 2012. Currently he is pursuing the Ph.D. degree in Electrical Engineering at Gujarat Technological University, Gujarat, India. His research interests include control of electric drive, application of MMC in renewable energy sources and multilevel converter.

Mukesh M. Bhesaniya

Mukesh M. Bhesaniya has received the B.E. degree in electrical engineering from the Sardar Patel University, Gujarat, India, in 2000, the M.Tech. degree in electrical engineering from the Indian Institute of Technology Kanpur, India, in 2009, and the Ph.D. degree in electrical engineering from the Indian Institute of Technology Bombay, Mumbai, India, in 2017. He has received "Academic Excellence Award" for the best academic performance during masters in Electrical Engineering from Indian Institute of Technology, Kanpur. In 2003, he joined G. H. Patel College of Engineering and Technology, where he is currently an Associate Professor in the Department of Electrical Engineering. He has published/presented number of research papers at National & International journals/conferences and he has been granted US Patent for invention in power electronics converter. He has also filed one national Patent for invention in power electronics converter. His research interests include power-electronic converters, HVDC, and flexible ac transmission systems.