Control of Seamless Transition between Islanding and Grid Connected Modes in WT Driven Doubly Fed Induction Generator-Based Microgrid

This work presents the seamless transition control strategies for rotor side converter (RSC) and load side converter (LSC) of wind turbine (WT) driven DFIG (Doubly Fed Induction Generator) -based microgrid. To decrease the battery size requirement and to increase the reliability of this microgrid, a solar photovoltaic array with boost converter are connected at the common DC bus of RSC and LSC. Moreover, the battery is connected at the DC bus to absorb the intermittency in wind-solar power generation. The control is presented to obtain the information of grid failure or its restoration to operate the microgrid either in islanding or grid connected mode seamlessly. Moreover, a modified wind-MPPT (Maximum Power Point Tracking) method based on tip-speed ratio is presented. It extracts peak wind power between specified speed regions of DFIG and operates at off wind-MPPT at below and above MPPT wind speed regions. The microgrid is simulated in MATLAB environment for various scenarios. Simulated performance is presented for the system during synchronization to the grid at constant wind speed and PV insolation, seamless transition between islanding and grid connected modes at varying winds, and PV insolations and system voltages-currents under unbalanced nonlinear loads. Moreover, the modified wind MPPT performance is presented for below MPPT wind speed. The microgrid voltages-currents, are obtained balanced and sinusoidal both in islanding and grid connected modes.