PR control based cascaded current and voltage control for seamless transfer of microgrid

This paper describes the cascaded current and voltage control for seamless transfer of microgrid with harmonic compensation according to load location. DG based microgrid is defined as a current source in the grid-connected mode and a voltage source in the islanded mode, respectively. Hence, it needs a robust control to supply the high quality power under both modes of DG based microgrid. But a connection of non-linear load and/or distorted grid can cause the system power quality degradation due to the produced non-linear current and/or voltage. Therefore, the PR control based cascaded current and voltage control which can be used under both modes simultaneously has been considered with a deliberate control topology in this paper. According to the load location, it can meet both non-linear compensation and seamless transfer between two modes. Also, a simple voltage restoration method has been added to solve the magnitude degradation of output voltage due to the practical PR control limitation and sometimes grid frequency change. Finally, proposed control methods which supply the power to the non-linear load under both grid-connected mode and islanded mode are verified through the PSIM simulation.