Cooperative compensation of unwanted current terms in low-voltage microgrids by distributed power-based control

This paper proposes a technique for the power flow control of three-phase four-wire low-voltage power systems, that aims at compensating the reactive and unbalance current terms measured at the point of common coupling of microgrids. It is based on a master/slave control architecture where a grid-interactive inverter, installed at the point of coupling between utility and microgrid, acts as master unit while the distributed energy resources act as slave units, allowing to fully exploit their available power capability. The proposed control technique ensures high power quality, smooth power exchange with the utility, and prompt and seamless transitions between grid-connected and islanded operation. The paper introduces the considered system architecture, overviews the power theory underpinning the control approach, and describes the proposed control technique. Finally, a real three-phase distribution system is considered as case study in simulation; the obtained performances in improving the overall power quality are reported and commented, in particular for what concerns the compensation of reactive and unbalance current terms under sinusoidal/symmetrical and nonsinusoidal/asymmetrical voltage conditions.