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Zero-Voltage Ride-Through Capability of a Transformerless Back-To-Back System Using Modular Multilevel Cascade Converters for Power Distribution Systems

This paper focuses on the zero-voltage ride-through (ZVRT) capability of a transformerless back-to-back (BTB) system intended for installation on a power distribution system with many distributed power generators. The BTB system consists of two modular multilevel cascade converters based on double-star chopper cells (MMCC-DSCC) and their ac sides are connected to a common ac mains via ac-link inductors. This paper provides an experimental discussion on the DSCC-based BTB system under voltage sags by using a three-phase 200-V 10-kW downscaled system. Experimental results show that the BTB system is equipped with ZVRT capability without causing any overvoltage and/or overcurrent even under the most severe voltage sags.