Transformerless Series Dip/Sag Compensation with Ultracapacitors using a new Multilevel Boost DC-to-AC Topology

Multilevel power converters that provide more than two levels of voltage to achieve smoother and less distorted ac-to-dc, dc-to-ac, and dc-to-dc power conversion, have attracted many contributors. This paper presents a new multilevel topology that can be used in series dip/sag compensators using ultracapacitors. This boost dc-to-ac multilevel topology has self voltage balancing of cells and may be derived from the generalized multilevel inverter topology presented by Peng. The new dc-to-ac topology is a unique solution that makes the use of ultracapacitors with relative low voltage ratings cost efficient for dip compensation on low voltage and high voltage lines. As there exists no neutral connection in the series dip compensator, little isolation restraints exist when using this inverter on high voltage lines. A functional 20 kVA single phase dip compensator based on the new multilevel topology is presented to verify the theory