A Power Flow Solution Technique for Autonomous and Non Autonomous Mode of Operation of Microgrid System

A power flow solution technique has been proposed for microgrid operating in isolated as well as grid-connected mode. The formulation is based on simple impedance matrix approach where the elements of the impedance matrix are the impedance of the power flow paths from the terminal loads to the node representing the point of common connection (PCC). Distributed generators in microgrid are modeled to operate either in droop controlled, P-V or P-Q mode. When connected to the grid, Distributed Generation (DG's) may be operated in any of the operating modes, but during autonomous operation, the droop controlled mode is followed. The bus interfacing the main and the microgrid has been chosen as a voltage regulated bus so as to facilitate seamless transfer from the autonomous to the grid connected mode of operation and vice-versa. Comparisons with existing methods are presented to show the accuracy and ability of the proposed method. Maintaining the PCC bus voltage at 1.0 p.u. helps to have an improved voltage profile and seamless transfer of the system between grid connected and islanded modes.