Circulating current suppression for a direct AC-AC modular multilevel converter in YDY coupling

A control strategy to manage the circulating current content in a Modular Multilevel Converter in direct AC-AC topology is proposed in this article. The converter is connected in three-phase YDY configuration which forms a closed delta path for free current circulation while keeping outsider waveforms with low THD content. Circulating current correction becomes necessary face to any kind of unbalance or even to small power transition. Simulations results show multiple frequency content in waveforms using a resonant corrector and performances against system unbalances.