Design and experiment of a back-to-back (BTB) system using modular multilevel cascade converters for power distribution systems

This paper presents an application of the modular multilevel cascade converter based on double-star chopper-cells (MMCC-DSCC) to a back-to-back (BTB) system for installation on 6.6-kV power distribution systems. The DSCC is characterized by a cascade connection of multiple chopper-cells per leg, leading to flexible circuit design, low voltage steps, low EMI emission, and low harmonic voltage and current. The DSCC-based BTB system is equipped with neither dc capacitor nor voltage sensor on the common dc link. The paper designs, constructs, and tests a three-phase, 200-V, and 10-kW downscaled system to verify and justify its operating principles and performance. Experimental and simulated results agree well with each other, showing a promising possibility of the DSCC-based BTB system.