Voltage-Source Control of DFIG in Standalone Wind Power-Based Microgrids

As the penetration of wind power increases, there is a growing operational demand on Wind Turbine (WT) systems to participate in microgrids frequency regulation. Traditional grid-connected Doubly-Fed Induction Generator (DFIG) control strategies are basically dependent on the power grid which is strong enough through the phase-locked loop (PLL). Traditional control strategies are not applicable to the weak grid with a relatively large short-circuit ratio (SCR). A new method must be introduced to let the wind farm actively respond to system frequency changes. This paper presents a control strategy which enables DFIG to behave as a voltage source. The droop curve is designed to realize the power sharing between DFIGs and battery energy storage system (BESS). Also, the grid frequency and phase angle required for coordinated transformation are no longer obtained through the phase-locked loop, but generated through the droop controller. Simulation results under various operation conditions are presented to verify the effectiveness of the proposed control strategy.