Transition Control and Operation of Hybrid Energy System

Abstract

—Microgrids are a modern class of power systems, consisting of loads and distributed generation resources within a defined electrical boundary. Distributed generation consists of renewable interfaced to the AC grid via inverters (Inverter-Based Resources or IBR) or units such as Diesel Genset (DG), which can be directly connected to AC bus. Microgrids are designed to be operational in both grid-connected and grid-forming modes. During the grid-forming (or isolated) mode, either the IBR or the DG operates as the voltage-frequency regulating unit, with the other operating in active and reactive power-controlled mode. For grid connection, a synchronization process is required, in order to prevent large power flow in either direction. A smooth transition is required from islanded mode to grid-following mode to avoid damage to loads. A transition control is also required, in case of planned or unplanned islanding of the system from the grid. In this paper, control for synchronization of microgrid to the grid is presented. The operation of a Hybrid energy system for grid-connected and island mode is described. DG control in grid-following mode or active power control is shown and a control is proposed for smooth transition from island to grid connected mode and grid-connected to island mode. The system is simulated and validated in MATLAB/Simulink.