An Observer-Based Inductor Current Control for a Bifunctional Three-Phase DG-Inverter

The worst-case scenario in distributed generation (DG) systems is an abrupt switch from grid-connected (GC) to stand-alone (SA) modes. This must be taken into consideration to protect the integrated power system when islanding happens. In the present paper, a robust sensor-less current control based on a digital Luenberger observer has been proposed to achieve a seamless transition from (GC) to (SA) mode. It reduces the system's cost and eliminates the need for communication and measurement sensors. The presented control is planned to function for both inner and outer loop voltages. Moreover, a phase-lock loop (PLL) based on a synchronous reference frame (SRF) is employed to ensure the required synchronization. The simulation results demonstrated the efficacy and precision of the discrete-time suggested control, ensuring a smooth transition in the event of islanding.