Hirofumi Akagi was born in Okayama, Japan, in 1951. He received the Ph. D. degree in electrical engineering from the Tokyo Institute of Technology in 1979. In 1979, he joined the Nagaoka University of Technology, Japan, as an Assistant and then Associate Professor in the department of electrical engineering. From 1991 to 1999, he was a Professor in the department of electrical engineering at Okayama University, Japan. Since January 2000, he has been a Professor in the department of electrical and electronic engineering at the Tokyo Institute of Technology.

   His research interests include power conversion systems, adjustable-speed motor drives, active and passive EMI filters, high-frequency resonant inverters for induction heating and corona discharge treatment processes, and utility applications of power electronics such as active filters for power conditioning, self-commutated BTB (back-to-back) systems, and FACTS (flexible ac transmission systems) devices. He has authored and coauthored more than 100 IEEE Transactions papers and two invited papers published in Proceedings of the IEEE in 2001 and 2004. The total citation index for all his papers in Google Scholar is more than 20,000 times. He has made presentations many times as a keynote or invited speaker internationally.

   He is the recipient of six IEEE Transactions Prize Paper Awards, 11 IEEE IAS Committee Prize Paper Awards, the 2001 IEEE William E. Newell Power Electronics Award, the 2004 IEEE IAS Outstanding Achievement Award, the 2008 IEEE Richard H. Kaufmann Technical Field Award, and the 2012 IEEE PES Nari Hingorani Custom Power Award. He was elected as an IEEE Fellow in 1996 and as IEEE PELS and IAS Distinguished Lecturers from Jan. 1998 to Dec. 1999.

   Dr. Akagi served as the President of the IEEE Power Electronics Society from Jan. 2007 to Dec. 2008 for two years.

    The modular multilevel cascade converter (MMCC) family consists of several members with different given names. These members with the family name “MMCC” have similar circuit configurations based on either single-phase full-bridge (H-bridge) ac/dc converters called simply as “bridge cells” or non-isolated bidirectional dc/dc choppers called just as “chopper cells.” However, these family members have different characters from a practical point of view. Among them, this talk pays attention to two specific family members with given names “double-star chopper cells (DSCC)” for grid connections and motor drives, and “triple-star bridge cells (TSBC)” for motor drives. Although the full names are “MMCC-DSCC” and “MMCC- TSBC,” they are called and treated just as a “DSCC” and a “TSBC” like countable nouns for the sake of simplicity.

     The DSCC is the same in circuit configuration as a specific modular multilevel converter called as an “MMC.” When a power electronics engineer uses the term “modular multilevel converter” in his/her technical paper/article or presentation, the other engineers, especially graduate students and young engineers, cannot identify the circuit configuration or may have a misunderstanding about it in the worst case. However, no misunderstanding would happen as long as the term “modular multilevel converters” implied general multilevel converters characterized by modular structure.

    This talk focuses on circuit configurations, controls and applications of both DSCC and TSBC for high-voltage grid connections and medium-voltage motor drives, showing experimental waveforms obtained from three different downscaled prototypes that have been designed, constructed, and tested in the speaker’s laboratory. Generally, a DSCC-based motor drive is different in application from a TSBC-based motor drive: The former is suitable for a medium-voltage high-power application, in which the load torque is proportional to a square of rotating speed, whereas the latter is suitable for a medium-voltage high-power application, in which the load requires the rated torque in a range from zero speed to the rated speed.