Control Design of Grid-Forming and Grid-Following Inverters with a seamless transition in Microgrid

The development of renewable energy resources has grown significantly in recent years. These distributed energy resources are typically connected to the grid through power converters, which can be operated in "grid-forming" or "grid-following" mode. But the large-scale integration of DG units has serious repercussions on the stability of the power system due to their low inertia compared to the synchronous generator. However, an appropriate control guarantees a dynamic, smooth, and fast converter behaviour in an island configuration and voltage-frequency support in grid-connected mode. This paper presents a control system for Grid-Following and Grid-Following converters for a grid-connected MG. The aim is to achieve a seamless transition between the Microgrid and the main grid, appropriate load sharing between distributed energy sources, and an improvement of system stability. The developed grid-connected battery storage system inverter has been designed to be able to operate in two different modes: grid formation mode and grid injection mode. The control strategy considers the control loops of Voltage/current, Frequency, and active/reactive power. The proposed control technique is presented and simulated under the MATLAB/Simulink tool. The simulation results demonstrate the efficiency and performance of the proposed control technique in eliminating voltage, current, and frequency fluctuations and also guarantee a seamless transition between the two modes.