A four-leg matrix converter based hybrid distribution transformer for smart and resilient grids

Abstract This paper proposes a novel four leg matrix converter based active distribution transformer (4LMC-ADT), which aims at empowering legacy distribution transformers with on-load voltage control, a fundamental requirement for the future grid. Resorting to a four-leg direct matrix converter and a series transformer, this work shows that a traditional transformer can be empowered with local on demand voltage regulation in the LV grid, series harmonic filtering, dynamic voltage restoration, and MV support through reactive power injection, therefore actively contributing to improve power quality in a LV micro-grid even under severely unbalanced load conditions. Non-linear Lyapunov based controllers are designed for the fast tracking of the LV voltage references combined with Euler Backward predictive controllers for the matrix converter currents. Experimental results show that the proposed solution is able to cope with balanced and unbalanced voltage sags, voltage swells and load step changes, guaranteeing fast and accurate dynamic response of the 4LMC-ADT.