Hybrid Microgrid with Advanced Complex Band Pass Filter Based FLL Control

This paper deals with the smooth transition between grid connected mode to an islanded mode and the stator terminals of the DFIG synchronization. The system considers battery, photovoltaic (PV) array and doubly fed induction generator (DFIG). In an islanded mode, battery-based grid forming converter (GFC) controls the voltage and frequency at the common connection point (CCP) or point of common coupling (PCC). The grid side converter (GSC) of the DFIG is connected to the CCP via the interfacing inductors. The DC-link between the GSC and rotor side converter (RSC) is regulated by the GSC control algorithm. The RSC control of the DFIG is divided into two parts. In the first part, the RSC control develops the controlled stator terminal voltage and frequency at the stator windings, which is connected to the CCP via a solid-state switch (STS). The second part of the RSC control provides the essential quantity of reactive power demand by DFIG and also extracts the peak wind power. The maximum PV array power is extracted and fed to the CCP via a voltage source converter (VSC) and the interfacing inductors. An advanced control complex band pass filter-based FLL (CBPF-FLL) control is used to control the battery-based VSC during the grid mode of operation. This control provides improved power quality like unity power factor and lower harmonics in grid current as per the IEEE-519 standard.